Adding length to For Next loop after starting

I wrote a script to add spacing between sets of rows with common data.

I set a = number of rows in the spreadsheet then use

For x = 2 to a

Every time I insert a space I follow it with

a = a + 1

but the script will only execute to the original value of "a" and not the updated one. How can I force the For Next loop to recognize that "a" has changed?

Thanks! I'll change it.

But just out of curiosity, is there a way to do it from top down?