In looking at the syntax for the DCount function, in the criteria clause, the value (text) has to be concatenated to the field name. I'm not sure this will work because it looks like you are trying to get a value from a report. I've never used a value from a report, only forms...... sooooo .......
But try this:
Code:
=Nz(DCount("[Category]","qryAttendanceHistorybyDept", "[Assoc Nm] = '" & Reports!rptAssociateAttendanceHistorybyDept![Assoc Nm] & "'"),0)
Note the delimiters in the criteria clause....