A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
It's not very obvious Ossie, but right click on the toolbar and choose customize, then grab one of the icons and move it a little to the right. When you release it a separator should appear to the left of it. Drag it to the left and the separator disappears.
Doesn't seem to work for icons on the extreme left of a toolbar or those with a separator already on their left (for inserting), although you can make an existing separator disappear by dragging left.