Need help with a formula that has 3 conditions

I am requesting help with a formula that I am flubbing.

In the enclosed file I need a formula in col D that will return the following:

Col D to return how many items still needed to ship to achieve 90% of the value in col B after subtracting what has already shipped (col C).

If Col B is zero then I just need 90% of col A.

If Col B already exceeds the value of 90% of col A I need to return the qty exceeded perhaps in brackets.

And then if qty to ship = zero, then just zero.

I hope this makes sense.

Thank you

Book1.xls