schedule date tracking

I want to do a workbook that will calculate the number of days it takes to build a product but take into account the days the construction is put on hold. Right now I have it set up with the stop date as =TODAY() unless I enter in a date and hold days are =A3-A2 and total days are =(A4-A1)-A5. This works but if I hold the job more then 1 time I would have to enter in more hold start and hold stop columns. Is there any way to trigger a hold by checking a box and unchecking it when it is ready to start and can it remember the dates if it happens multiple times?

start holdstart holdstop stop holddays totaldays
1/1/2007 1/5/2007 1/10/2007 2/6/2007 5 3