My Apologies Daryl, I Think i helped confuse you.
Perhaps an easier way to do this will be to create checkboxes with the department ID as the value:
department 1:<input type="checkbox" name="email[]" value="1" />
department 2:<input type="checkbox" name="email[]" value="2" />
department 3:<input type="checkbox" name="email[]" value="3" />
department 4:<input type="checkbox" name="email[]" value="4" />
and use DataAssist search to filter your users table on the department ID column. in data assist search, create a new filter using the List Fileter type on the email form element to filter the deptID column. Set the Default where to " 0 != 0" so the recordset will initially be empty.
Then in Universal Email, set the to tab to use the recordset loop and set the trigger to if the recordset is not empty.