activating macro within a cell formula

If you want to run a macro based on certain cell conditions being true or false then you can use worksheet events. Right click the sheet tab, click View Code. You'll see the worksheet code module. In the left hand combo box choose Worksheet. In the right hand combo box choose Change. You can then write code that will be activated each time a user changes a cell value and then check for various conditions. Make sense? If not, post some more details of your particular problem.

Regards,
Dax.