Using graphs from websites in macros

Hi

I've got a problem that requires me to use the graph that I attached. I retrieve this graph from a website.

Is there a way in which I can simply display the letter 'B' in a cell on a spreadsheet when the blue line crosses the top red line and similarly display an 'O' when the blue line crosses the bottom red line?
I reckon it's a pretty heavy problem and the only solution I can think of is using Visual Basic code. Any ideas on the code or alternative solutions?

Thanks!