If statement help

[Excel15]

I'm starting in Row B. The statement needs to say that if row F says "High" then give me a 1 and if not then leave it blank. The next cell down in Row B says the same thing except it says that if the corresponding cell in row F says "High" then add 1 to make it 2 and so on down row B. It's probably much easier if someone opens the attachment and looks at my note and the issue I'm having then me trying to explain. I highlighted where I'm having the issue and added a comment to explain. Any help would be much appreciated.

Cheers,

[ChemistB]

=IF(F4="High", MAX($B$3:$B3)+1, "") copied down