I very much doubt that it is possible. You will probably have to follow the VCD instructions on this website from scratch.
You can't convert anything to other format without losing quality -- whether you're doing VCD to DivX, SVCD to DivX, DivX to SVCD, DivX to VCD or whatever. This is because all of these formats are "lossy" formats -- they take less space because they drop certain part of the video data out in order to reduce the size of the video -- and so, when you're converting from one lossy format to another, the other conversion has less data that it can play with in order to get the best results. But you can convert DivX to VCD, follow this guide: http://www.afterdawn.com/articles/archive/divx_with_subtitles_to_vcd.cfm