Automatically adding a value to a different cell depending on data entered.

I am trying to get excel to automatically add a value in the next cell depending on the entry. For example if I enter 1a in cell A1 i want it to add 11 in the cell next to it. If I add 1b I would like it toadd 13 in the cell next to it and so on.

Each value has a numerical value, w=3, 1c=7, 1b=9, 1c=11, 2c=13, 2b=15, 2a=17, 3c=19, 3b=21, 3a=23, 4c=25, 4b=27 and 4a=29.

Any ideas qould be much appreciated. Thanks

Thanks for your help. Have since worked this one out. Thanks for getting back to me though

Andy