Nested IF Statement? Expert needed to review

Hi Wyn

In Cell AZ174 of the attached, I am trying to set up a way to ensure an expense claim on a finance facility does not exceed the limit of the facility given previous drawdowns and future costs to complete.  The formula I posted if effectively trying to put into practice the following statement: 

If (Drawdowns to date + Expenses this month+ Future Costs to Complete) < Facility Limit, Expenses this month, IF( ((Facility Limit)-(Drawdowns to Date)-(Future Costs to Complete)) > 0, ((Facility Limit)-(Drawdowns to Date)-(Future Costs to Complete)) ,0))

Outcomes expected:

If the claim this month does not result in the facility cap being breached then the result is the full claim

If the claim this month does mean the cap is breached then the claim is capped to the extent the facility becomes fully drawn (so part but not the whole claim is the result)

Alternatively if the facility has reached its cap before this months claim then the claim this month would be zero.

Your help is greatly appreciated