combo incremental search

[Temple Software <temsoft sancharnet in>]

Hello,
I need the combobox to do incremental searching. Is it possible? that is, when 
I press say, 'S' the selection should position automatically to the word 
starting with 'S'. Though in Windows this works by default, I cannot do this 
in gtk+ under Linux. Help!

The absence of this singular feature prevents me from porting a fairly large 
business application from Windows to Linux.

Mani. M