I'll assume you're using a form. Place a combo box (cboState)with a label that says 'Select State'. You can pick the combo box value up and use it to refine both the data diplayed and the report.
Private Sub cboState_Click()
On Error GoTo NoState
Dim strState as String
strState = Me![cboState]
Me.Filter = "((qryUsed.State = '"&strState&"'))" 'This assigns the filter
Me.FilterOn = True 'This turns the filter on,use this if you want to filter the form and display the results. Otherwise, just assign the Me.Filter and use it when you open the report (see below)
Exit Sub
NoState:
If Me![cboState] = Null Then Exit Sub
End Sub
DoCmd.OpenReport stDocName, acPreview, , Me.Filter
Have a happy programming day!
L