It's still not clear if this is what you want, but if you want the current
date and time to be inserted into the CallDate field everytime you update
the value in the Disposition field then use someting like this in the
After Update event of the Disposition control;
Me![CallDate] = Now()
If you only want the current date and time to be inserted if there is
*not* already a value there then use;
If Nz([CallDate], vbNullString)=vbNullString Then
Me![CallDate] = Now()
End If
As Dave mentioned, if all you really want is the date then use Date()
instead of Now()