Cheapest deal to Europe I could find from DEN is $ 547.31 to Amsterdam. I doubt a lot of offers will come during this weekend, because flights to Europe (LON, PAR, FRA), but also to Denver seem to be busy.
BK CODE W -
DEC28 UA465 DEN-IAD DEP 10:58 ARR 16:10*
DEC28 UA946 IAD-AMS DEP 17:55 ARR 7:20
DEC30 UA947 AMS-IAD DEP 12:30 ARR 15:05
DEC30 UA963 IAD-DEN DEP 17:40 ARR 19:31
Total price including taxes $ 559.14.
* could be replaced to get the lowest price ($ 12.00 cheaper) with:
DEC28 UA1532 DEN-IAD DEP 6:35 ARR 11:41.
Total miles: 10,438 (+ elite bonus)
I can't find a return on Sunday.
Maybe you find a better domestic deal, but in that specific weekend, I couldn't find anything else to Europe...