Nigel,

In a combo the event that fires when the value changes is the When. Also, if the combo's rowsource is alias or fields there is no need to do a seek as the combo moves the records pointer by itslef, one anly needs a form refresh.

In addition, to the original poster, using a buffermode of 3 will cuase tableupdates to fire whenever the record pointer moves, you might want to consider using 5 as the buffer mode.