You can use a scroll bar to change the value of a cell that contains a variable number. For a good example of using scroll bars to control cells that drive a chart, download this Projectile Motion Spreadsheet.
Add a Scroll Bar to a Worksheet
1. Open the Forms Toolbox by going to View->Toolbars->Forms
2. Click the Scroll Bar icon in the Forms Toolbox
3. Click and drag on the spreadsheet to create the Scroll Bar
Link a Scroll Bar to a Cell
1. Right click the scroll bar and select Format Control
2. Make sure the Control Tab is selected and you’ll see
3. Set the options as desired and hit OK
Summary of the Options
Minimum Value: The Minimum Value of the Linked Cell
Maximum Value: The Maximum Value of the Linked Cell
Incremental Change: The amount to increment the linked cell value when the Arrow on the scrollbar is pressed
Page Change: The amount to increment the linked cell value when the Scroll Bar Face is clicked
Cell Link: The address of the cell to be linked to the Scroll Bar
