So, I went into Settings/Per application and selected Add. T
Then I browsed to the Excel.exe and selected it. When a workbook was open, the title bar wasn't skinned with the skin I had selected in Styles.
Instead, the grid area had been "skinned" with the main color of the skin.
Add Edit: I tried a few more skins , and nothing changed in Excel.
On a side note:
When I try to create/Edit a texture for the Start menu, WB crashes.