Problem with Update Error '3144'

I Cannot find the correct syntax to fix the problem i'm having. i'm using a update query to change a variable.  The strFieldName is the field name A1 throught A80.
    Dim txtName As String
    Dim strFieldName As String
        txtName = Me.txtSelectedText1.ControlSource
        strFieldName = Mid(txtName, 4, 3)

        DoCmd.RunSQL "UPDATE VehicleEquip SET VehicleEquip.( " & strFieldName & " )  = False;"

the code works if there is a spacific field (eg."UPDATE VehicleEquip SET VehicleEquip.A41  = False;")
but i need it to work for all of them.

i'm aware that i can create a recordset and then loop through them, but this seemed easier, although now its not.....
thanks
~B~