Another attempt in the new revision... (if you don't use svn replace the "FixedCols" of the previous patch by "LeftCol").
BTW, quite some time after I wrote this, I feel that setting borders of neighboring cells is still very confusing. What do you think? Suppose one cell, say (r=6, c=6) with a border at the right, and the left neighboring cell (r=6, c=7) gets a border at the right as well, aren't you expecting the left neighboring cell to have both a left and right border? In the worksheet this is true, but in the worksheetgrid, the left border of (r=6, c=7) is removed.