Informix XWindow/Xterm Question

I have a question regarding key assignments. We have an application written in Informix 4GL that is character based. We are migrating to a Sun platform providing Xterminals as user workstations. We have in the past been on a Sequent with the users using Wyse 50 character based terminals. The application is being rewritten for a Motif GUI but the development will take about 6 more months. In the interim until this development is done, we have to run the application on the Xterminals using an Xterm session to do so. Now to the actual question, the application uses several function keys(19 or so to be exact) and we need to be able to pass these on so the app can recognize them. I have mapped the function keys using xmodmap(even looked at it using xkeycaps to make sure I did it correctly). After mapping the keys to the appropriate function key, I tested them all using xev( the event monitor and everything seems to work fine while using xev). I then captured each of the appropriate key sequences sent by each key. I added these to the "xterm" termcap entry and assigned the correct function key assignment to each sequence. However, when we run the app, it does not see the function keys. I am sort of at a loss at this point. Does anyone have any ideas, suggestions or see where I am missing something or screwed up somewhere? I would certainly appreciate any insight anyone could give. And yes, I am running xmodmap "filename" in the user .xinitrc so the keymapping is being used. Thanks for any who can help and I will repay those who can with a great thanks and any help/services I could provide to you. Thanks again.....