As you give no details on your "RF modules", it is not easy to advise. At 432 MHz, try to find where the antenna is, and turn it away from a target. You can also cover the module in aluminum foil to prevent it from radiating too much. Leave only a narrow slit in the wrap, and see what happens.
If aluminum attenuates too much, try to enclose the module in a lossy enclosure, like a metal box with a hinged lid; then by opening or closing, the lid, you can adjust the range.
The best way, if your RF module is a transceiver with a common antenna, I would disconnect the antenna and connect another one through an adjustable attenuator.