I am trying to select a range by using either a do until or do while loop

I have a value in colum "a" and need to loop through the collection till the
value in a is ="".

The range will be starting in eg B7 to g9 range("b7:b9").select
A7 wil start as the active cell so
The code will be something like this:
activecell.offset(-1,-7).select ' this will select a7 so the first value
is known
range(activecell.offset(1,0):activecell.offset(7," unknown").select
I need to know wht the unknow value is.
Now it must loop down till value = "" is established
How do i determin the 2nd value ie "b9"

Ie I do know the starting point of range, i do know the amount of colums in
the offset but not the amount of the rows, which is determind but the amount
of rows looped down


Thanks