There's a little misunderstanding here.
MKV (Matroska) is a container. It wraps a number of video, audio and subtitle streams into one file.
DivX is a video encoder. It's one implementation of a certain video codec.
MPEG-4 Part II is a video codec standard. DivX for example creates MPEG-4 Part II compatible video. XviD is another encoder that does this.
See this question for more about that: What is a Codec (e.g. DivX?), and how does it differ from a File Format (e.g. MPG)?
Now that we've cleared that up, there's not much sense anymore in "converting MKV to DivX". In fact, the MKV file you have could already include DivX-encoded video – who knows? You can analyze existing files with MediaInfo to make sure.
So, you seem to be unsure about what result you even want. DivX-encoded files can come in a number of containers, but AVI, MP4 and MKV are most common. If you want to create a DivX-encoded file, then you have to live with the fact that it will end up in an AVI, MP4 or MKV container, no matter what tool you use.