Hi Bash,
If you don't want overlapping, I would execute an aggregate before adding the new record, with something like this for condition
aggregate.enddate >= form.begindate
AND aggregate.begindate <= form.enddate
AND aggregate.id <> form.id
If this query returns empty, you can go ahead and add/update your form record.
using >= or simply > is debatable, if one ends on same day as other starts, is that considered overlap or not...
Dorine