The easiest way to pass information from the calling script (the one with the Place Call step), to the answering script (the one queuing the callback call), is to use Set/Get Enterprise Call Info steps.
In fact, the way in which the Set/Get Enterprise Call Info steps work, is by attaching data to a Contact. The Contact in the calling script, the one you use in the Place Call step, is actually the same Contact in the answering step, the default --Triggering Contact--. So, actions performed on one, are actually performed on both.
Example
Calling Script
Place Call (callback_contact)
Success
Set Enterprise Call Info (callback_contact) my_variable = "my value"
Answering Script
Accept (--Triggering Contact--)
Delay 3 sec
my_variable = Get Enterprise Call Info (--Triggering Contact--)
If (my_variable == "my value")
True
/* This should be true */
Note the delay in the answering step. This is not accidental. You are essentially firing two scripts to run in parallel here, and so we have a timing issue between when the calling script has set the variables, and when the answering script is trying to read them.
Tip for the pros: You can actually use this feature to understand when the Agent answers the call from the answering script, and then in the calling script poll the Enterprise data for a flag to be set to true. E.g., is_answered. This avoids the repeating message thing of "This is a callback call. Press any key to blah blah blah"
It's confusing, no doubt, so just post back if this still doesn't make sense, and I'll keep helping.
