If you only want points for the single upcoming stay, you have two options:

1. If you have enough time between your last miles-earning stay and the upcoming points-earning stay, and all completed stays have posted to your account, feel free to change your earning preference in your online profile. You must keep the preference set to earn points until the points post, so if you are immediately following up with another stay that you want to earn miles, this will create a tangle.

2. If this single stay is intended to be a singular event earning points while in the middle of a bunch of miles-earning stays, you can tell the hotel at check-in to "force" the stay to earn points. (You will even get your platinum amenity bonus points, which you normally don't when earning miles). The desk clerk may not know how to do this, but the manager should. If there is any doubt, you should ask the manager to get on the phone with the MR folks. You want to get this straightened out at check-in.

I was told about this "force points" technique by a Marriot Plat Line rep, and I can confirm that it did work for me just a couple of weeks ago. The reason why I did it was because I had completed all 13 DL miles stays, but the last few had not yet posted. I was doing back-to-back stays, so I didn't want to change my preference to points and screw up the pending miles posts. Yet I didn't want to earn miles anymore, since I had maxed out the promo.