System Not Recognizing Date Input

I have a form where the user inputs a date into a combo box and then selects a command button.


There are two options:
1. The user can select an exiting entry (by date from the combo box) to edit a existing entry.
2. to create a new entry they enter a new date (not in the combo box).
Then the user selects a command button.

The command button has an onClick macro where the value in the combo box is checked (IsNull([Combo40]))

If the "IsNull([Combo40])" is true a message box is presented saying the date field is blank.

The problem is (finally) if you enter a new date "3/3/04" and forget to hit the enter key the system doesn't recognize the entry, in other words the "IsNull([Combo40])" evaluates to TRUE.

We currently have the msgBox remind the user to hit the enter key but that seems a little low tech. Is there anyway to look at the field and see the data even though the user forgot to hit the enter key??

Thanks