Filter Report based on Selection from Form

I have a form with 4 combo boxes set up and a run report button. I
would like to pass the selection from the combo boxes to the report
select statement. Below is my code from the "run report" button. I am
currently getting a type mismatch error. Any help would be great. I
can't seem to find a straight forward way to do this anywhere.

Private Sub Run_Task_Tracker_Click()
On Error GoTo Err_Run_Task_Tracker_Click

Dim stDocName As String

stDocName = "Task Tracker"
DoCmd.OpenReport stDocName, acPreview, , "[emp_name]= &
[Forms]![TaskTracker2]![Employee]"

Exit_Run_Task_Tracker_Click:
Exit Sub

.