DCOUNT, VLOOKUP not working for my project

Hi, all,

I have a list of about 300 unique names on sheet1 and a spreadsheet with about 17000 rows, representing one week of account activity, on sheet2. These rows contain multiple occurrences of each name, along with dates, times and minutes of use. On sheet3 I have broken down the range of dates and time frames I am trying to isolate into a number of criteria tables.

I need to determine the activity for each user within a designated time frame. I need a both a count of occurences and a sum of the minutes.

I've been trawling the net all morning and struggling away with DCOUNT, IF, VLOOKUP and a pivot tables, but so far have failed to find a solution. DCOUNT leaves the names out, VLOOKUP and pivot tables leave the time frame out, and IF doesn't seem to work at all.

Any suggestions?

Edited to add, this is the type of thing I am trying to do, which does not work:
=IF('sheet2'!A:A='sheet1'B5, DCOUNT('sheet2'!,12,'sheet3'!$B$3:$E$7), 0)