How to record ditigally on old comb tv/vhs

Question

I have a digital converter box hooked up to my 1996 combo TV/VHS. I can't figure out how to tape my programs since the digital stations are 12.1, 15.1 etc and it seems to only record on the standard channel 12, 15 etc.is there some way to fix this problem as i don't want to purchase a new tv.Thank you for your helpMichelle Yates