WorkSHEET or workBOOK ???
You can use the worksheet_activate event for a worksheet
Right click on the sheet tab and choose "View code"
then, change the right hand drop down to "Activate" and pop the name of the macro you want to run between the start and finish
...and delete the selection change event sub that will be automatically generated when you hit "View Code"
For workBOOK - use either the workbook_open event (go to VBE, double click on the "workbook" icon in your "projects" list) or create a sub called Auto_open in a standard module Rgds
Geoff
Si hoc legere scis, nimis eruditionis habes