Here it is, I tried changing (the one in red text) this
DoCmd.OpenForm "frmVehicleMaintenance", , , "VehicleId=" & Me.txtbox_VehicleId
to this
DoCmd.OpenForm "frmVehicleMaintenance", , , "txtbox_VehicleId=" & Me.txtbox_VehicleId
still same error message that I've attached here