Formula Help Needed
 

I need help with a excel formula. I am looking for a formula that will populate a calf number after entering a cows number. If the cows number is
OA12 the O=year born(2000) A=generation(-=first calf A=2nd calf) 12= cows #

Cow 1 Gen. 2 Gen 3 Gen 4 Gen 5 Gen 6 Gen 7 Gen 8 Gen
OA12 2-12 3A12 4B12 5C12 6D12 7E12 8F12 9G12

3-74 5-74 6A74 7B74 8C74 9D74 0E74 1F74 2G74

Any help will be greatly appreciated. Thanks