Hide Rows based on value
 

I would like to have a numeric value in cell D7 to indicate how many rows
beginning 12 - 71 are hidden from view automatically.

Column B numbered 1 - 30 with additional row in-between for cosmetics which
indicates number in row directly above.
B12 = 1
B13 = 1
B14 = 2
B15 = 2 and so on

so if D7 = 7, I would like for rows 26 through end of document to auto hide.

Thanks for help