Synchronising two datagrids

I'm trying to sychronise the scrolling of data in two
datagrids that are bound to the same dataset. I have
managed to synchronise the scrolling of the scrollbars by
subclassing the datagrid class and setting the values of
the grid's vscrollbar and when the scroll event is raised
on one grid I set the vscrollbar value on the other grid.

Using this technique can quite happly move both scroll
bars by moving one or the other but the data displayed
only moves when the user clicks on the vertical scroll bar.

Can Anyone provde me with the missing peice of information
to complete the jigsaw?

Thanks

AndyP