Specific macro or VBA code to hide and unhide rows

Hey everyone,

This is my first question here, but I used the forum a lot before. Each time I found the answer, so I have good hopes for this one too
I found a couple of similar threads about this, but none worked for me (probably because I don't know how to adapt the code).

I have an empty col A
I have a col B with names in it.
I have a lot of other col from C to ... but those don't really mather here

In col B, beside names, I have empty cells too ... These are for the users to add names.
e.g.
B3 to B11 = names already filled in
B12 to B17 = empty cells

My question about this is:

If B12 is empty, B13 till B17 should be hidden rows.
From the moment someone fills in B12, B13 shoud auto unhide, B14 till B17 stays hiden.
If someone wants to fill in an extra name in B13 too, B14 = unhide, B15 till B17 = hiden
And so on, and so on ... Note: B18: always visible because that's a new set of values that always must be visible.

Hope that someone gets me, and that my English wasn't too bad
PS: it's for Excel that I'm using @ work, so it's 2007.
The attachment is another version of Excel, that's my home edition.

Thanks in advance !

Kristof