Conditional Format a cell returning a date based on a cell containing a formula)

So I have a workbook with 2 sheets, On Sheet 1, there is a field that calculates the expiration date of something based on text in its description (B3=description, F4=opened on date, G4= expiration date)

G4=IF(ISERR(FIND("Long",B3)=TRUE),F4+"72:00",F4+"100:00")

Sheet 2 has the same layout as Sheet 1.
on Sheet 2 I want to show the values from Sheet 1 column G in the sheet2 column G. (thats easy)
I then want to conditionally format F3 (new opened date) on sheet2 to change red if it is more than 30 mins away from the expiration date.

I think the issue that I am running into is that cell G3 is a formula. If I try something like >G3+"00:30" it does not respond at all, but if I change G3 to a regular date, it works.

Thanks

where would I put that formula? in the conditional formatting part? Im confused.
and I think i still will run into the same problem, that G3 is a formula and it doesnt like adding a value to a formula.