Switching row labels and data from multiple columns around

It seems like there could be a relatively easy solution to this, but my knowledge of excel lingo is so poor that I'm having trouble googling relevant stuff.

I have a table of courses (1,2,3) and teachers (a,b,c,d), which I'd like to dynamically flip (kinda transpose, but not quite) by teacher. A course can have multiple teachers (or none) and a teacher can teach multiple courses. If that's what it takes, I'll be happy to do VBA too.

Any nudges toward the right direction?

This is what I have:

1	c
2	b	c	d
3	a

This is what I'd like to see dynamically updating:

a	3
b	2
c	1	2
d	2