Joining 2 fields to 1

[dodge20]

I am using ISQL 7.2 I am trying to create a form where 2 codes (ttran_code and atran_code) fields from my subscription table match up with the tran_code field from my trans_code table.

Here is an example

a2 = tcc_subscription.ttran_code = tran_codes.tran_code,upshift,queryclear;

a4 = tcc_subscription.atran_code = tran_codes.tran_code,upshift,queryclear;

But this gives me an error saying that thre tran_codes.tran_code has already been used. Is there any way around this? I thought there was a lookup but I am not sure.

Thanks for your help

Dodge20