else 1=1 is killing you. I would try
if instr({JCJMPM.udMarketType}, {?MarketTypes}) > 0 then something

this code is trying to find the start of the market type in the parameter. Of course there is the problem of 1 being found in 12 and 15...so it is not perfect.

The next step, and I don't know if it is possible, is to break your input parameter into an actual array of values, and then your original code would work as long as you point it at the array that you just made.