GridSplitter resize problem[WPF]

I have a grid with two columns (one with "*" width and the other is auto) and a gridsplitter between the columns.

I have expander in my top-right corner (they open left-to-right). the columns expand and collapse properly with the expander, until I use the gridsplitter. T

The left column always stays at the size set by the gridsplitter. any idea how i can force the column to shrink back since the expander is collapsed?.

Thanks...

Please let me know if you are able to solve the problem. I am still scratcing my head.

Can you post the xaml code that you are using?