Restricting data of a field(fipex) from search help

Hi Experts,

    Whenever the user press f4 on fipex field am getting all entries for that particular.

Here the requirement is we need to restrict the data which is coming from search help(f4),

How we can restrict this? Is this restriction is possible through search help exit enhancement,

ISo please any one give idea about search help exit enhancement,if possible post the sample

code for this is greatly appreciated.

                                Thanks in advance..

Regards,

Kranthikumar