In FMP7, you can use the Auto-Enter Calculated value and unchecked "Do not replace existing value of field (if any)".
Put his formula in Specify for PhoneNumber [text] =
"(" & Left(PhoneNumber;3) & ")" & Middle(PhoneNumber;4;3) & "-" & Right(PhoneNumber;4).
Hope it helps
For the import of vCard and vCal you can use the substitute function.
On Mac OS X, I use the Terminal and grep. But this solution depends on the platform you're working on.
For the sepcifictions of the vCard and vCal, check this good source http://www.imc.org/pdi/
BR,
Sarpedon