Category: Repeating
Syntax: Extend ( nonrepeatingField ) 
Parameters:
nonrepeatingFieldAny nonrepeating field (a field defined to contain only one value).
Data type returned: Text, Number, Date, Time, Timestamp, Container
Description:
Allows a value in nonrepeatingField to be applied to every repetition within a repeating field (most commonly a calculation field). Without using the Extend() function, only the first repetition of a repeating calculation field will properly reference the value in nonrepeatingField.
Examples:
Given a number field RepCommission, defined to hold three repetitions, a nonrepeating number field (SalePrice), and repeating calculation field (SalesCommission), defined as follows:
Round ( RepCommision * Extend ( SalePrice ); 2 )
RepCommission 
SalePrice 
SalesCommission 

.10 
18.00 
1.80 
.12 
2.16 

.15 
2.40 
Without the Extend() function, only the first repetition of SalesCommission would have returned the correct value.