The way I read it; you want to use the 200.3MHz microphone with the 234MHz receiver - by changing the 234MHz receiver. If this is the case; the only way I see this working out with the numbers you provided is if the 234MHz uses a 21.4MHz IF and not a 10.7MHz IF. The 21.4MHz IF, although not as common as the 10.7MHz IF is still pretty common. To check this you have to look at the markings of the IF filter on the 234MHz receiver - it should be either a ceramic filter or crystal one.