Calculating Vessel Utilization in Budget Projections

I am trying to calculate Vessel Utilization which in itself is not posing any problems but what is causing me problems is the fact that I am trying to do multiple calculations. I am trying to determine the number of days worked, Idle days, Repair Days in the same spreadsheet. I am trying to calculate the # of worked days based upon me changing the % of utilization but also to take into account a manual entry for Repair days and Shipyard Days.

The attached spreadsheet shows what I am trying to accomplish and only the areas in yellow are editable cells, the rest should be calculated with a formula.

Can someone point me in the right direction.

Thanks
Ray

Your suggestion works basically the same is what I was doing. This all works great when doing a straight calculations on say 80% of days worked out of a 31 day month. Where the problem comes in is when I add days in repair and/or days in shipyard instead of reducing the number of idle days it will reduce the number of days and it keeps the idle days just as they were which is not the correct way. Hope this helps to clarify my problem.

Thanks
Ray