dynamically modification of a table (IE only)

I need to modify on a javascript event a table (<table border=0 width="95%" cellspacing=1 cellpadding=2 bgcolor="#808080"> ) which contains on a column "high" cells (<td rowspan=n bgcolor="#ffffff" align=center>&nbsp;</td> ).
The problem is that when I insert a new row under the "high" cell, IE allows me to increase the rowspan of the "high" cell, but when I insert a new row above the "high" cell, IE cannot increase the rowspan of this cell.
Can you figure out a solution?

I also thought about inserting some "fake" cells there, but I cannot figure out the style of the table and of the cells, considering that I have cells of other background colors in the table, and that I cannot change the look of the page - it's a client request .