Running a query from a form

Allen Browne saved my brain yesterday with his date validation query (see
"Booking out a Guest suite , avoiding double booking in Access" posted 14/02)
his query works without question. I now have a related question. If i input a
start date i need to check the start date is not part of an already booked
period. then assuming it isnt i then need to check the dates from that start
date till the date i enter next being the end date. If i must i can just
input both and check at the end but how do i send the dates to the query and
get either a ok or not ok result.