I am trying to to use excel to calculate how much to bet depending on varying odds to always get a profit of 100 back...but I have been struggling to get the formula right and would really appreciate someone's help!

Basically, if the decimal odds is 2.00 and I want to make a hundred pounds profit I would have to bet £100, but how do I make a formula in excel that calculates this for me so that I can do it for any odds? It seems so simple, but yet I can't seem to get my head around it.