Percentage calculation between two dates.

Hi everyone ,

Hope you are doing well.

I need some help on one excel formula, I searched on internet but couldn't find it.

Suppos I placed a purchase order to a company for some materials, and the delivery to our warehouse is four weeks from the date of awarding the purchase order, however if the vendor fails to deliver the materials as per agreement, then 1% of the value of each item in the purchase order will be deducted per week, maximum to 5% of total value of each item.

For instance, if the purchase order placed on June 1st and the agreed delivery schedule is 4 weeks, means June 30th, however the vendor delivered after 8 weeks, so how would I calculate the difference between agreed delivery date VS actual delivery date in percentage? So I can make the deduction accordingly.

I know there are several ways to do this, but just wondering if there's a specific formula to do this exercise more easy and efficiently.

Hope you got my pint.

Looking forward for your positive response.

Regards
Kamran