#NA - ERROR handle in formula

Assume three columns A, B and C. Columns A and B can contain text, numeric values or #NA.

Column C should summarize the columns A and B

eg If A2=123 and B2=#NA the result in C2=123

or If A2=#NA and B2=K2-123 the result in C2=K2-123

or if A2=#NA and B2=#NAthe result in C2= (empty cell)

or if A2=123 and B2=K2-123 the result in C2=123 (the same as cell A2)

Is it possible to handle #NA in a formula?

Yes. There are ISNA and IFNA functions (that are suggested, e.g., when one writes NA in Function Wizard).

Thanks! It works for me! (but the formula for managing this, did not get small). Is it possible to get the formula IF NOT NA or IS NOT NA?

NOT(ISNA(A2)) or IF(ISNA(A2);...then...;...else...)