I've been using the half point calculator to compare the price between different spreads and totals. I've found it very useful for Football and Baseball.

What i'm wondering is how would someone go about either manually calculating the difference in value between two different spread prices (say Book A is +6.5 -105 and Book B is +7 -115).

Also would it be feasibly possible for someone like myself with an average knowledge of excel to put together a spreadsheet that would do half point calculations for other sports? (Rugby League is one that I have in mind)

Any advice would be much appreciated!