>how to design a combo which search on more than on column.
>like itemcode or itemname depending on user choice.
>Rajesh

A grid seems to me more appropriate for this purpose. For instance, the individual columns have click() events, etc. I don't know where I would make the user select data in a ComboBox.

In Visual Extend, both sorting and search on more than one column are implemented, through grids. For instance, to sort on Column1 + Column2 + Column3, the user would double-click on Column1, then Control-Click on Column2, then Control-Click on Column3. For incremental search, the user goes to Column1 and types the combined expression for one or more columns.