Interception of two non linear graphs

Hallo all,

this is my 1st time ever to post a thread on any forum so I hope I won't write anything inappropriate (or bad written).
I am trying to make an Excel data that automatically shows the interception point of two curves.

I am posting my example and I would like you to comment on it.
It seems to me that this solution does not always give the same result for the interception point.
Example:
if I put another start-end in the column "input"
- although curve "A" is always the practically same curve no matter where it begins or ends - the input cells are there to make the x-value grow equally in the same step
-by changing the start and end the step changes also but the curve does not change much
- i deleted all formulas of curve A and B because the file was too large.

Please comment