Using Message Boxes

In your programs and macros, you can use message boxes to display information or ask for confirmation of a task. By using an If structure or Select Case structure linked to the value that the message box returns, you can determine which button in the message box the user has chosen. You can use this value to direct the program flow appropriately.

The syntax for displaying a message box with VBA is as follows:

MsgBox(Prompt[, Buttons] [, Title] [, Helpfile], [, HelpContext])

Prompt is the only required argument for the MsgBox statement. Prompt is a string that is displayed as the text in the message box.

Buttons is an optional argument that specifies the buttons that the message box displays, the icons that the message box displays, the default button, and the modality of the message box. Each of these four elements can be specified with either a value or a constant. You use the + operator to join the values or constants together.

Your first choice is the buttons the message should display. Your options are shown in Table 26.3.

Table 26.3: Command Button Constants

Value	Constant	Buttons
0	vbOKOnly	OK (the default if you omit the Buttons argument)
1	vbOKCancel	OK, Cancel
2	VbAbortRetryIgnore	Abort, Retry, Ignore
3	vbYesNoCancel	Yes, No, Cancel
4	vbYesNo	Yes, No
5	vbRetryCancel	Retry, Cancel

Next, you can choose which (if any) of the standard four message box icons to display. These choices are shown in Table 26.4.

Table 26.4: Standard Message Box Icons

Value	Constant	Displays
16	vbCritical	Stop icon
32	vbQuestion	Question mark icon
48	VbExclamation	Exclamation point icon
64	VbInformation	Information icon

Next, you can set a default button for the message box. If you choose not to set a default button, VBA makes the first (leftmost) button in the message box the default—the Yes button in a vbYesNo message box, the OK button in a vbOKCancel message box, and so on. Table 26.5 gives you the choices of default buttons for a message box.

Table 26.5: Message Box Default Buttons

Value	Constant	Default Button
0	vbDefaultButton1	The first button
256	vbDefaultButton2	The second button
512	vbDefaultButton3	The third button
768	vbDefaultButton4	The fourth button

In theory, you can choose whether to make the message box application modal (the default) or system modal. Application modality means that you can take no further actions in the application until you dismiss the message box; system modality means you can take no further actions on your computer until you dismiss the message box. In practice, this system modality does not work—even if you use the vbSystemModal argument, the resulting message box will be application modal. (See Table 26.6.)

Table 26.6: Message Box Modalities

Value	Constant	Modality
0	vbApplicationModal	Application modal
4096	vbSystemModal	System modal

Finally, you can now specify some new information for your message box. The Help button can now be automatically added, the message box window can be set in the foreground, and two options that are most useful when working with Project in a language that reads from right to left. Text can be right-aligned, and text can read from right to left. (See Table 26.7.)

Table 26.7: Message Box Options

Value	Constant	Displays
16384	vbMsgBoxHelpButton	Adds Help button to the message box.
65536	VbMsgBoxSetFore ground	Specifies the message box window as the foreground window.
524288	vbMsgBoxRight	Text is right aligned.
1048576	vbMsgBoxRtlReading	Specifies text should appear as right-to-left reading on Hebrew and Arabic systems.

Title is an optional string argument specifying the text to appear in the title bar of the message box. In most cases, it’s a good idea to specify a Title argument to make it clear which procedure has caused the message box to appear. If you do not specify a Title argument for the message box, VBA will display "Visual Basic" in the title bar, which is singularly uninformative.

Helpfile is an optional argument, specifying the Help file to invoke if the user summons help while the message box is displayed.

Context is an optional argument, specifying the topic to display in the Help file. If you use the Helpfile argument, you must use a corresponding Context argument.

For example, the following statement specifies the message box shown in Figure 26.8. This message box has Yes, No, and Help buttons, with the No button the default, and displays the question mark icon.

MsgBox "Delete all selected tasks?", vbYesNo + vbDefaultButton2 + vbQuestion   + vbMsgBoxHelpButton, "Delete Selected Tasks"

Figure 26.8: A custom message box

The previous statements simply display the message boxes described—they don’t let you know which button the user clicked. To return a value from a message box, declare a variable for the value and set the value of the variable to the result of the message box:

Dim intResponse as Integer intResponse = MsgBox "Delete all selected tasks?", vbYesNo 

VBA stores the user’s choice of button as a value in the Response variable. Table 26.8 shows the values and their corresponding constants.

Table 26.8: Message Box Response Values

Value	Constant	Button Selected
1	vbOK	OK
2	vbCancel	Cancel
3	vbAbort	Abort
4	vbRetry	Retry
5	vbIgnore	Ignore
6	vbYes	Yes
7	vbNo	No

The following statements use a Select Case structure to establish which button the user chooses in an Abort/Retry/Ignore message box:

Dim AbortRetryIgnore AbortRetryIgnore = MsgBox("Abort, retry, or ignore?", vbAbortRetryIgnore + vbCritical Select Case AbortRetryIgnore Case vbAbort   'Abort the procedure Case vbRetry   'Retry the procedure Case vbIgnore   'Ignore Case Else   'Nothing should produce a Case Else here End Select

For simple Yes/No or OK/Cancel message boxes, you can use a straightforward If statement:

If MsgBox("Is it raining?", vbYesNo + vbQuestion, "Weather Check") Then   MsgBox "It's raining." Else   MsgBox "It's not raining" End If 

Use the Buttons Arguments in Order for Easy Reading

The Buttons arguments do not have to be in the order discussed here—they will work in any order. For example, VBScript is smart enough to work out that the 1 in the following statement, rather than either of the 0s, refers to the type of message box:

MsgBox "Proceed?", 0 + 16 + 1 + 0, "Bad Value"

Better yet, you can mix values and constants, if you want; therefore, the following three statements are functionally equivalent:

MsgBox "Proceed?", 1 + 32 + 256 + 4096, "Bad Value"

MsgBox "Proceed?", vbOKCancel + vbQuestion + vbDefaultButton2 + vbSystemModal,
"Bad Value"

MsgBox "Proceed?", 4096 + 32 + vbOKCancel + 256, "Bad Value"

That said, your code will be easier to read if you use the standard order: Type of message box, icon, default button, and then modality. It will also be easier to read—though a little longer—if you use the constants rather than the values.