I think what he is asking for is an actual energy type attack that projects off the melee weapon. Wraithstrike does not do this and neither does bloodstorm blade. Throwing your sword at someone and then having it return does not quite meet the feel of ranged energy attack.
The most logical thing to do would be to enchant a melee weapon to produce an area effect attack when swung properly. Easy ideas are cone of "Insert X Energy Type Here", or many of the line attacks. This gets fairly pricy though.
A level 3 lightning bolt cast at level 5 caster level at will on a melee weapon should cost around 30,000g. Not really feeling it for 5d6 use activated. Even for a command word it would still cost around 27,000g.
Another simple solution; allbeit not as visually fun, is to adapt the Bloodwind spell from SpC to affect melee weapons instead of natural weapons. Now you can attack with "invisible" melee strikes from up to 20ft away. I seem to recall a villain from the Ruroni Kenshin series using compressed air waves as a form of ranged attack. An at use bloodwind weapon would cost roughly 2,000g. Some may argue that since it has a duration of 1 round you multiply the cost by 4. If this is the case then the cost is 8k. But since the books specifically uses the phrase. "rounds" I take it by RAW it means plural and thus a spell lasting only 1 round is exempt from that ruling.
So in short:
Spend a chunk of change to add X cone/line spell as a command word or use activated effect to a weapon.
OR
Modify the bloodwind spell to work with melee weapons. Although 2k gold to increase your reach with any melee weapon by 20ft seems somewhat like swiss cheese. XP
