Dynamic numbering

Hi, I'm trying to create dynamic numbering for headers in an Excel model. The file attached has a Header and then two types of sub-header. The number for the headers is 1, 2, 3, etc... Numbering for the sub-headers is then 1.1, 1.2, 2.1, 2.2 etc... Finally I also have a 3rd sub-header which would read 1.11, 1.12, 2.11, 2.12 etc...
I simply want to be able to copy and paste the formula, which will calculate what the header number should be.

That's a fantastic formula - thank you