After checking a bit on the United website, I found a saver award for 60,000 miles + $96.20 if you can leave one day earlier and fly RT Newark--Brussels. Here are the details.

Wednesday, June 20:

UA 28 Newark--London Heathrow; lv 7:35 PM arr 7:40 AM next day
SN 2094 LHR--Brussels; lv 10:05 AM arr 12:20 PM

Thursday, June 28:

AC 833 Brussels--Montreal; lv 10:40 AM arr 12:20 PM
UA 4968 Montreal--Newark; lv 2:53 PM arr 4:46 PM

I realize that it's not ideal, but it seemed worth calling it to your attention.