locating a function to a special adress

please help me

I want to place my wait() function in util.c from 4000H adress;

I wrote "?PR?wait?util(0x4000)"
in Options menu>LX51 Locate> User Segment

I got *** ERROR L108: SEGMENT IN LOCATING CONTROL CANNOT BE ALLOCATED error message.

what is this, how can I locate my functions in uV3?