[Users] Modify Refer-To: URL

[Frogger]

When a REFER is sent from ua1 to ua2 I need to modify
the "Refer-To:" URL.

ua1 will send the refer using the alias 222 which is
for username 5551212

Therefore, ua2 needs to receive 5551212 in the
Refer-To:.

How can I modify the Refer-To field prior to
forwarding the request to ua2?

Thanks!!

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