It's usually acceptable to bump a thread after not receiving a response for a day, I would say 12 hours at the very least.

=SUMPRODUCT(--(D5:D10<E3+14),--(E5:E10<>"VACCANT"))

OR

=COUNTIFS(D5:D10,"<"&E3+14,E5:E10,"<>VACCANT")

Not tested the last one.

Dom