Using Absolute Cell References
When you want a formula to consistently refer to a particular cell, even if you copy or move the formula elsewhere on the worksheet, you need to use an absolute cell reference. An absolute cell reference is a cell address that contains a dollar sign ($) in the row or column coordinate, or both. When you enter a cell reference in a formula, Excel assumes it is a relative reference unless you change it to an absolute reference. If you want part of a formula to remain a relative reference, remove the dollar sign that appears before the column letter or row number.
Use an Absolute Reference