Conditional plot labels

Hi all,
I'm trying to do multiple graphs in a window like this:

        ___  ___   ___
ylab  |__|  |__|   |__|
        ___  ___   ___
ylab  |__|  |__|   |__|
        ___  ___   ___
ylab  |__|  |__|   |__|
         xl     xl     xl

If I try to put the labels manually, some graphs become smaller than
other and the output is really ugly.
In the thread title I put the word "conditional" because I'm trying to
do a function, and in that function I want to print ylabels if the
plot positions is at first column of the graph matrix, and xlab if the
position is at last row of matrix.

How can i achive this two things?

Thanks for your help

CdeB