I believe that the correct syntax would be:

MATCHCOUNT(Trim({Trx Acct}), "16231", "16232", "16233", "16234", "16235...)

If any one of these 5 digit numbers exist as a {Trx Acct} in any record then the result is true (> 0). I'm not sure if the order of processing is the entire table or individual records.

Which table are you using with the field Trx Acct?