I’ve tried this trick with the NovoLog (NovoRapid) Flexpen, the Levemir Flextouch pen, and the Lantus Solostar pen, and none of those pens will let you dial back the plunger. I even tried disassembling them and resetting the plunger manually, but something in the mechanisms of these pens is adamant that they are a one use only device. Did manage to get one Solostar to kinda sorta work, out of several I tried, but it was so wonky there is no way I would have trusted the dosage.
I did, however, salvage almost all of the disposable vials (they are delicate outside the pen!) and I am waiting for delivery of one of the Luxura HD pens from www.canadadrugs.com to determine if they can be refilled and used in that device, as described here.
Filling your own pens
If anyone wants to have a go at some empty Solostar pens (with the vials removed) to see if they can figure out a way to reset the plungers so that the pens still work, send me a msg and we can work out a way to get them headed your way.