How do I detect GridRangeInfoList crossing column boundaries?

I have a GDBG that I want to allow the user to multi select rows within a column and then perform a right mouse click action on all rows selected. I''ve got that all working fine, but my problem is how do I prevent them from selecting cells from multiple columns? Each column in the grid allows a different right mouse click action so having cells selected from multiple columns would be confusing. What I would like to do is if the user has crossed column boundaries, clear the previous range. I''m having a hard time finding an event to use to capture this situation. Also note they could be selecting via a drag or shift/ctrl-click. Any idea what event(s) to use?

Try handling the SelectionChanging event and cancelling it if e.Range is more that 1 column wide.

private void Model_SelectionChanging(object sender, GridSelectionChangingEventArgs e)
{
	if((e.Range.IsCols || e.Range.IsCells) 
		&& e.Range.Left != e.Range.Right)
	{
		e.Cancel = true;
	}
}

Works beautifully if you are dragging, but does not handle the ctrl-click. This is a great start though, I should be able to figure out the rest from here. Thanks for the prompt reply!!!