Insert / Delete rows

I've been searching for this for some weeks now, but I just can't find it. I'm a moderate excel user, but not really into VB. This is my dilemma:

I'd like to create a variable list. If a number is entered into B7 (see attachement), I would like that number of rows being inserted below. Starting at A8. But I would like the list to be variable. So if a lower number is entered, the rows would be deleted. And I would be great if the formulas could be maintained.

Is this possible? Thanks in advance!

ps. Sorry for my bad English, I'm Dutch.