best thing you could try is a local mitre10/bunnings and get some wall shelving brackets, concrete anchors (for your wall) and some hooks, shouldn't be too hard to rig something up.
Im assuming your projector screen came with the usual wall/ceiling brackets?
Any reason that you can't hang direct from the ceiling?
In our last house, I had to get into the roof to put some timber up in the right spots, but was easily able to get it hung from the ceiling in the right place, out 150mm or so from the wall so that the screen would pull down infront of a plasma.
take a picture of the bracket in the link to the shops, there'll be something "close enough" if you want to do it today
Like sen8or said, I would go and get a small shelving bracket and the find a hook you can bolt to. You will need a hammer drill to put a hole in your concrete too. 6mm rawl plugs is what you want. Then you just put normal gib screws in to them.
But again, like sen8or said, why not just chuck hook in the ceiling? If it is an outside wall might be a bit tight in the ceiling but will be much tidier overall.