Gridview Checkbox

Hi,

I am using checkboxes in one one column of gridview in asp.net with VB.In header also for check all option.When i click on the header check box all checkboxes in the grid view are being selected.But what i want is when checkall is clicked and one of the checkbox in the grid is deselected then the checkbox in header also is to be deselected.Can any one please help me.

Thank you