mazilo, you're over complicating it;
-call your voicemail
-press 5 for advanced options
-listen to the menu and go to record a greeting
-record whatever number greeting you want saying "hello, i'm unavailable, leave your msg" or something less informal
-go to the advanced options menu again and press select greeting
-select the one you just recorded
now the ones calling you will hear something even better than an automated voice!!
now... if you still want to do it with automated voices, set a var (not sure if you also need to export it) with the destination number on the moment the initial call is done (the one that catches the XXX-XXXX-XXXX long number) then use that var.
good luck!