Extend a part

I have a part that I've imported from NX. I want to extend the part (make it longer). Rather than sketch on the surface and use the convert entities to create a sketch and extrude to the necessary length, is there a way to just offset the surface to the required length? I tried offset surface but this only offset the surface it does not extend the part.

Thanks

Kris.

SolidworksParts And Features