I now see a problem in the Original Row Source property you posted. The combo name was not in there. So you would have to change bound column for combo1, as sugested, and paste this into the rowsource of Combo2
Code:
RowSource:SELECT tblDepartment.ID, tblDepartment.DepartmentName, tblDepartment.Portfolio FROM tblDepartment WHERE (((tblDepartment.Portfolio)=Forms![Combo Form]!Combo1)) ORDER BY tblDepartment.DepartmentName;
Considering the Row Source you first posted, the VBA option would be to build your SQL string like this
Code:
Private Sub Combo1_AfterUpdate()
' Update the row source of the Combo2 combo box
' when the user makes a selection in the Combo1
' combo box.
Me.Combo2.RowSource = "SELECT tblDepartment.ID, tblDepartment.DepartmentName, tblDepartment.Portfolio" & _
" FROM tblDepartment WHERE tblDepartment.Portfolio)='" & Me.Combo1.Column(2) & "'" & _
" ORDER BY tblDepartment.DepartmentName;"
End Sub