Hello Andrew,

If E1 contains your Account no search value and D1 your Date search
value:
=INDEX(C2:C5,MATCH(D1&"|"&E1,A2:A5&"|"&B2:B5,0))

The "|" construct protects you against lookup values like
54321 and 2-4-09
vs.
5432 and 12-4-09

Regards,
Bernd