ST Transaction Set code to GS Transaction Code

I am looking for a mapping service that will provide me the GS transaction Code (GS01) when I pass the ST code (ST01) and vice versa. Basically, we need to build GS and IC envelopes over STs that are persisted in TN. We want to use one service irrespective of ST transaction without hardcoding for each txn set. I know webMethods EDI batch process does generate the appropriate GS code for a given ST edidata. So is there any standard wM service or wM api that does this trick. This way, I dont have to worry about creating a mapping service covering all the possible EDI Txns and support for future releases.