Adjustable Project Task Scheduler

[Zness]

I am attempting to design a spreadsheet to schedule production tasks. This scheduler would be able to answer the question of:
"What day is the work on project 'x' going to begin?"

This essentially means that I want to have a task scheduler where each project is assigned to a date, and also allotted the portion of the day that it takes to complete that task. When the day is 100% full of projects, the following project's start date rolls over to the next day and on down the line.

My idea was this:

Project 1: .3 days, 1/6/2013
Project 2: .3 days, 1/6/2013
Project 3: .3 days, 1/6/2013
Project 4: .25 days, 1/7/2013
Project 5: 1 days, 1/8/2013
Project 6: .5 days, 1/9/2013
Project 7: .5 days, 1/9/2013
Project 8: .25 days, 1/10/2013
and so on....

I have been working on this for a few days and have come close, but my model is still not working. Has anyone attempted to do this before?

And to top it all off, when the boss comes in and says "Hey! Project 8 has top priority now!" I need to be able to copy/paste or move Project 8 to the top of the queue and have the table recalculate.

Here is what I have so far

http://2.bp.blogspot.com/-1rMCudz9doo/UstCv60yZBI/AAAAAAAAB2Q/KnuuqseM7tE/s1600/Task_Date_Rollup.PNG

I am totally willing to scrap what I already have for a more robust solution

thanks,
z