SMK,
Sorry; I misread your question.
Although it's a bit of work, you can do what you want (sort of) by setting
the ControlSource of a textbox to:
=IIf(Hour([YourTimeFld])>=12,DateAdd("h",-12,[YourTimeFld]),[YourTimeFld])
Lay the textbox directly over one bound to your field. Set the latter's
Visible property to No in design view, and the other's to Yes. By default
then, the form will display the value formatted as you wish, albeit in a
control that is non-editable.
If you wish to be able to edit the field, you can use the Enter event of the
calculated control and the Exit event of the Bound control to toggle the
Visibility (and therefore, editability) of the two controls:
' Calculated Control Enter event code
With Me![YourBoundControl]
.Visible = True
.SetFocus
End With
Me![YourCalculatedControl].Visible = False
' Bound Control Exit event code
Me![YourCalculatedControl].Visible = True
' Set focus to next form control, since you're finished editing
Me![YourNextControl].SetFocus
Me![YourBoundControl].Visible = False
Hope that helps.
Sprinks