I can't say for sure, the HDMI port of the GTX 950 would have to be able of transferring analog video signals, and far from all HDMI ports can do that.
If you already got a HDMI to VGA converter, it's worth giving it a shot.
If it doesn't work, you'll have no other choice than using a DVI to VGA converter instead. Sorry I can't be of more help here.