Let start in stages, will start with one text box for the filter

Create a MainForm called - MainFilter
Create a text box in the main form, called - department
Create a Button the main form to active the filter

Create a sub form Called- SubFilter, and bound it to the table (record source)
select * From TableName
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At that stage when the form is run all the records in the sub form will apear

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Now add the filter to the SubForm using the record source
select * From TableName Where department = Forms![MainFilter]![department]
Or Forms![MainFilter]![department] Is Null

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On the On Click  event of the button write
Me.[SubFilter].Requery

Make sure that the subform control has the same name as the subform

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Now,try it , anter a value in the text box and press the button.
If that will work well be able to move to the next text box