Don't worry, this isnt too complicated. Lets say you want to use 2 textures, both 256x256 in size (they have to be the same size). Using any kind of graphics program, put them side by side. Your combined image should now be 512x256 pixels in size. Now you set up your matrix as usual.
now use "prepare matrix texture 1,256,2,1"
i.e Matrix 1, both textures are 256x256, there are 2 horizontally and 1 vertically.
Your first texture will be tile 1, the second tile 2.
Now, say you wanted a part of the matrix from x-position 10, to z-position 30 to be textured with tile 2, you would use:
set matrix tile 1,10,20,2.
then update the matrix as usual.
If I have time tomorrow, I will create a sample prog and post the link on this forum.
Whatever I did I didn't do it!