Wherever this gets posted, the answer is: No, there is not a simple way to upgrade from knoppix 3.6 to 3.7 other than replacing your 3.6 installation with 3.7. You can keep your 3.6 installation up to date by upgrading the individual applications to the latest versions.
Check first to see if there is a big enough difference from 3.6 to 3.7. It may not be worth the effort, especially if you have put a considerable amount of work into setting up your 3.6 installation. I am still using 3.4, I found minimal difference from 3.4 to 3.6. I haven't looked at 3.7 yet, I am currently upgrading instead to kanotix because it is less buggy than knoppix.