It would help to know the make, model, and year of your van, and if you can see it the make of door (probably Hartal - most are.)
If it is Hartal the panel on the door around the window is easily removed by popping the clips out at the bottom. The blind comes out with the panel.
Do a bit of Googling or You-Tubing - there are dozens of videos on how to do that sort of thing. The spring return on the pull-down blind in the door window of our Unicorn S4 Seville became detached. I found a video of how to do it, dug out some superglue, and followed the instructions to the letter - and it worked!!