[Serusers] using variables, modifying "FROM" field

Hi, In our telephony network, telephones have a private telephone number and a public telephone number. I want the CLIP to be the private telephone number when calls are made to other company phones, and CLIP to be the public telephone number when calling the outside world through the gateway. eg: private number: 911/XXXXX <-> 02/52XXXXX public number 921/XXXX <-> 03/204XXXX and so on. I know I could hardcode this in SER using something similar to subst("/^From:."(.*)sip:([^@]*@[a-zA-Z0-9.]+(.*))$/From: "+\1sip:+\2/"); (got that from a previous mail :)), but my numbering plan is too complicated, and changes too often to implement it that way. I'd prefer it to be in some database table which I could access through some exec-statement. For Uri translation this would be easy with the exec_dst statement, but I can't see any way to put the outcome of an exec statement in some sort of variable, which I would then use in the subst() statement. Or am I overlooking something??? Thanks, Piet