How to check authorisation for field in VA02

Hi,

I have developed one screen having some fields on it.

Those fields are stored in VBAP.

I need to check the authorisation for those fields using 'AUTHORIRY_CHECK' function module for the user to chage those fields.I have created the separate authorisation object for those fields.If the user is not authorised the field should be disabled along with the message to the user that he is not authorised.Where should i write the code for that?

How should i do this?

.

Regards,

Deepak.