In the Microsoft Excel Objects folder within your VBA Project, select
the sheet that contains the cell that you want to run the macro.
Place the code in the Worksheet_SelectionChange event of that sheet.
Or, you could have the main code stored in a seperate module and
simply call it from the selectionchange event. Example:
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
If Target.Address = "$G$5" Then MsgBox "you click it!"
End Sub
--Or--
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
call ClickedSub
End Sub
HTH
-Jeff-