If I understand the question, this might work for you
=SUMPRODUCT(--(Sheet1!A2:A10=A2),--(Sheet1!C2:C10=C2),--(Sheet1!B2:B10=B2-TIME(0,3,0)),--(Sheet1!B2:B10<=B2+TIME(0,3,0)),Sheet1!E2:E10)

I put you data in row 1 for the two sheets (with headers) and made up some
extra data down to row 10. You will need to adjust the ranges. Unless you
have Excel 2007, SUMPRODUCT cannot use full column ranges as in A:A. The
third and fourth terms specify that the times in Sheet1 must be within
plus/minus 3 mins of the time in Sheet2

best wishes
--
Bernard Liengme
Microsoft Excel MVP
http://people.stfx.ca/bliengme

"Twiggy" wrote in message
...
Hi
Please help.
I have two sheets as follows:

Sheet 1:
Date / Time / Number Dailled / Duration
/Cost
22/1/10 10:00 01234123456 00:01:57
0.789

Sheet 2:
Date / Time / Number Dailled / Duration
/Extension
22/1/10 10:02 01234123456 00:01:56
1501

I am trying to put the cost of the phone call against the relevant
extension
on sheet 2 that has dialled the number dialled. Obviously I can match the
number dialled in both cases, and the date, but there may be calls made to
that same number by that same extension on that same date but at a
different
time, so I need to incorporate the time into the formula, to say if the
date
matches and the number dialled matches, and the time difference between
the
two is (say) less than 3 minutes (as that is about the difference I am
looking at) then give me the cost of that call in the column next to the
extension number on Sheet 2.

Sorry for the waffle but can anybody help.
Thank you