Format cells based on condition

I would like to insert a series of shaded cells based on the number in another cell.
In the attached spreadsheet you will notice a number in cell B21, to the right begining at B4 and going to H6 you will find the series of cells in reference. I would like these referenced or group of cells be entered the number of times that B21 has referenced. 1 group of cells if the number 1 is entered into B21, 2 sets of grouped cells if the number 2 is enter into B21 ect. up to 6 times
I have number 4 entered into B21 on the attached sheet1 and number 2 entered into B21 on sheet2 so you can see how it needs to be layed out.
I am not a VBA writer.
Any help on this would be greatly appreciated.
Thanks in advance
Keith