Calling WebApp from Metadata capture screen

System

TS 6.1 Win2K

This seems to be more of a JavaScript problem than TS.

I've a metadata capture screen with a call-out button.
I want to call a web-app (basically a JSP) running on another machine.
This webapp allows the user to select some value and asks him to click submit.
On submit, this value should be sent back to calling app i.e. the metadata capture screen.

If my app is running on the same app server as TS, I can pass the value back using JavaScript. Something like
calloutForm.elements_name.value = "abc"

For the webapp running on another server, its giving me a JavaScript security error and not returning the value back.

How do I go about it (setting a form element's value from an application running on another machine).

TIA