Extending the range of electro magnets? Can it be done?

Extend the range? Why do you mean? If by range you mean the distance at which it exerts a force, well, that's already infinity.

 

You can extend the reach by using an intermediary piece of metal, along the line of picking up a chain of paper clips.

 

Ummm...yeah. I'm pretty sure he means he distance at which it produces a measurable, non-negligible force that is capable of doing something. If so, then russ waters is right. The larger the current in the coil, the stronger the magnetic field will be at any given distance.

 

well if you can design the electromagnet by yourself - the force should be proportional to the number of turns of the coil

 

An electromagnet with iron as a core will saturate at some value of the field strength. At that point you get no more help from the iron in increasing the field strength and cranking up the juice will have much less effect. At this point it's better to increase the diameter of the core and the coil. (and crank up the juice as well to keep the field strength constant).
a 1 cm^2 coil with a field strength of 1T will produce the same force at 5 cm as a 100 cm^2 coil with the same field strength will at 50 cm.