Any question answered...

I'm confused...

Range("b3:B" & LastRow - 1).Select
Selection.FormatConditions.Delete

Selection.FormatConditions.Add Type:=xlExpression, Formula1:= _
"**=IF(AND(ISBLANK(CH3)),(CQ3>=CF3+365))**"
Selection.FormatConditions(1).Interior.ColorIndex = 3

Are you aware that there are two languages mixed in together here?

Most of it is macro language (visual basic), which is a procedural language - the macro works step by step through it obeying the instructions. It uses the dot notation as addresses to get hold of bits of the worksheet and do relevant things to them.

The bit in bold it excel spreadsheet formula language. Spreadsheets are magic, not procedural: all formulae are continuously evaluated. (Behind the scenes they do a lot of bookkeeping to work out which formulae a data change can affect, and ripple the re-calculation out from the change to only those formulae and only when the change happens). It is also a very regular language: all the functions come in prefix form, i.e.: AND(condition1, condition2, ...), FUNCTION(list of inputs to function). Unlike VB which does things like 'condition1 & condition2' where the AND function is in the middle.