I am not sure if it will work but the character code in Excel for that symbol is 83
so the formula would containg, the function, char(83) but it may just return a capital S, you would have to change the font.
There is an add-in available here
http://www.cpearson.com/excel/chars.htm, but I am not sure if it will insert the symbol as you want it again without change the font, to Symbol.
Maybe someone knows otherwise?