>That's what I want, but it is a messy calculation to get there (adding the columns plus 12 for each column - doesn't seem safe to me). I was wondering if there was a property on the grid that contained the correct value for this.

Why 12? I would have just assumed that:

nWidth = 0
for each loColumn in This.Columns
	nWidth = nWidth + loColumn.Width
endfor
?nWidth

would do it.