Cancell Update event

[TruthAndBeauty]

Hi folks.

Scenario:
Continuous form.
Each record has one editible field, a date field bound to a table. The user enters a invalide entry into record #1 and immeidately clicks on the entry field on record #2.
-------------------------------------------------------------------------------------------
Validation (psuedo code) :
entry can be blank (null) or
if IsDate(entry) and [entry] between date1 and date2 then
update (save entry)
else
error message,
cancel save,
put/leave cursor on the record/field that failed validation
End

I couldn't place all the validation on the Validation property and then make it work. I put the validation in the Befroe Update event but I don't know how to cancel the Update event from saving if the vlaidation failed. It's important that the cursor remains or is returned to the invalid entry control.

I suspect there is a very easy way to do this and I've lost my way. Suggestions? Thanks.