grid range_select is slow for large grids

Hi,
I'm using the method described in the wiki page
http://wiki.wxpython.org/index.cgi/wxGrid
section 4.2 to collect the current selection when recieving a RANGE_SELECT event. This works but is slow for large selections.
Is there possibly a faster way for the simple case that you select whole columns by clicking (and dragging) on the col labels?
Regards, Christian