Next time you visit your real, ie. Ranger Trainer in TNN, you will be given the option of training, after that converasation at lvl 5 you should see Return Blade become available
I have successfully used return blade after a parry and a block. But the style can be interrupted easily. Make sure you have it hot keyed to say the least
Use Return Blade after successful BLOCK. Low fatigue cost, medium bonus damage, small attack speed and movement speed reduction in target, lasts 3 seconds tops.