Is there any way to give a format to arithmetic computations in Objective-C?

Question

i want to define something similar to a computation method:

NSString *format = @"%d + 1";

In my code i want to do something like:

int computedNumber = sum(format,5) => the result should be 6.

could you give some suggestions? thank you

EDIT: or something similar to: NSNumber *no = [NSNumber numberWithFormat:format,5];