Excel question

I am trying to build a formula in Excel 97 to insert a timestamp in a cell when other cells in that row is modified. (i.e. Insert date/time in cell B10 when any of cells B1:B9 are modified) This file will be used on a Palm Pilot (syncronized with Documents To Go). Since this is going to be running on a Palm, I am limited to worksheet functions only, I cannot use a VBA macro because they are not supported on the Palm. Any ideas would be greatly appreciated.