Formula based on matching and unmatching Dimension

Hi,

I am struggling with this for last one week. can anyone help me

I have 2 data providers Q1 contain Material and Q2 contains ISBN. I am merging both at report level.

(Material and ISBN is list of numbers and both are string)

eg

Material ISBN Formual 111 111 A 121 122 B 123 124 C

Now I want to write a formula based on that saying that

if (Material =ISBN Then “A” (Eg:111)) ElseIf (if the number only in Material then “B”(eg. 121,123) Else (IF the number only in ISBN then “C”(eg.122,124 )))

anyobe have solution to this approcej