Offset and Countif with dynamic Range

I've got the following function: A2-OFFSET(A2,5+(COUNTIF(B2:B7,"X")),0)

When I place an X within B2:B7, and the offset happens, it now does A2-A8, which is what I want, but I also want to be able to take into account that X and have the range change from B2:B7 to B2:B8. Which means if I now place an X in B8 that the result will return A2-A9. And so on. Is this possible?

Hey Pepe, thanks for posting! However, that array formula doesn't seem to be giving me exactly what I'd like.

The original formula I've got accounts for any X's within 5 cells of B2, however, I'd like for it to keep extending the range if X's appear within those 5 cells. And to keep accounting for any X's that might continue to appear in the dynamically increasing range.

I thought maybe my explanation before was a little brief, so for anyone else that might know how to solve this problem, I've attached an example document which hopefully illustrates what I'm trying to do. Cheers