Conditional Formatting

In my excel worksheet with a calendar, there are 3 columns - Start date, end date and area.  I want to highlight the dates between the start and end date in different colors depending on the area calculated. 

 

For my calculation, I have considered the initial area to be 12-meter square. The excel sheet will calculate the area required(eg. a book) with its available width and length and the number of items. It inserts the remaining available area by subtracting the required area - total area (12).  The conditional formatting should also check the multiple areas inserted for the same time period should consider the total area and should display the appropriate shade in the calendar.