Send called number

Hi,
calling a specific extension starts a CCXML application.
CCXML application must “understand” the called number, but it receives the extension number.

inbound route --> set destination extension 999

expected:
extension 999 ( CCXML application ) --> CalledNumber = real called number

obtained:
extension 999 ( CCXML application --> CalledNumber = 999

– OR –

expected:
extension 1 --> call extension 4
extension 2 --> call extension 4
extension 3 --> call extension 4
extension 4 --> Call Manager CCXML application --> CalledNumber = extension1, extension2, or extension3

obtained:
extension 1 --> call extension 999
extension 2 --> call extension 999
extension 3 --> call extension 999
extension 999 --> Call Manager CCXML application --> CalledNumber = 999

How can I configure freepbx to obtain the expected result?