NCM scripting @ Sign

I am trying to create configs template so that I can define a varilable and call it in command line but doenst work, can some one help:

.PARAMETER_LABEL @CUSTOMER

3 Digit customer ID

string @CUSTOMER

vrf context CUST-@CUSTOMER-WDATA

Above srcipt says that @CUSTOMER-WDATA doesnt exist, how can I tell script to only read CUSTOMER and add -data to it? Also what language NCM uses for scripting?

Thanks

Omair