any way of dividing phlox?

If you can easily divide them, after shaking off any soil, round the tub would be suitable this year. Take them out again in the winter and divide them up again.

Phlox subulata does not normally lend itselff to division like Phlox paniculata, leastways not in my experience. (But then I only have about 30 of them). Two ways of getting more plants, cutings, dead easy any time they are growing and layering. Take a shoot and peg it down, they root within weeks.
Some times if you have bought a large plant then you might be able to detatch pieces. If you do, you need to trim back the top growth if the roots are not that well established.