Exchanging into DVC through RCI is very doable, provided you learn how the system works, and do whatever is necessary to be successful.
The two threads Charles gave you above will give you some good insights.
One key is to understand your own timeshare and how it works in RCI.
RCI has two completely separate systems -- RCI Weeks and RCI Points -- and it is important to know which one (or both) your timeshare uses. An "ongoing search" is an automated waitlist available only within RCI Weeks. If you are using RCI Points, you will have to check availability daily.
DVC typically deposits availability between 7 months and 5 months from check- in date.
Another key is to understand your "currency" of exchange. Some timeshares (DVC, Wyndham, Hilton, and others) exchange on a fixed points grid. In that grid, a particular size unit will be a certain number of points during a particular season, regardless of where the destination resort is located.
The other system commonly used is Trading Power Units (TPU). TPU attempts to balance supply and demand for both the underlying timeshare and the particular unit you want at a particular time. For that reason, TPU is a moving target; for DVC, I have seen TPU's ranging from mid-20's to near 60, so there is a wide range. If your timeshare does not have enough TPU, you can combine weeks to raise your TPU to where it needs to be.
If you let us know which timeshare you own in St. Martin, and the TPU if you know it, someone here will probably to give you more specific advice.
DVC is definitely doable, and worth learning the ropes to get.