wxGrid, border around cell[0, 0] / prevent multi-row select?

hello,

I've a simple wxGrid, where I set selectionmode to SelectRows,
and disabled editing.
This works, accept,
cell [0,0] always has an extra border around it.
How can I get rid of that border ?

and a second question
How do I prevent multi-row select ?

thanks,
Stef Mientki