Batboard

Hello.
I have 2 radios GM900. The first one tx and rx on 432.500Mhz and the
second on 432.900Mhz for example.
How can i interconect them so that when the first receive something on
432.500 to transmit to the second GM900 to transmit that on 432.900, like
a repeater ?

tnx a lot

i know there is a r.i.c.k. to do this ... but i need information too! ...