Unable to create object with Oracle pacakge function in IDT

Hi All,

I am trying to define an object with predefined Oracle package function.while validating the below given example it throws Warning"Invalid Expression".

Even without validating the object I went ahead to use the object in a Query but again it end up in error-ORA-00904: "EC_PKGE"."CONVERTNUMBER": invalid identifier

Is there any restriction in IDT to use with oracle package function. Please help

Thanks

Jabir