Cant be void? Script Help!

[Loveridge]

void OnStart()
{
AddEntityCollideCallback("Player", "lighttrigger", "lighton", true, 1);
}

void OnEnter()
{

}

void lighton(string& lighton, bool true, bool true);

Apparently this cant be allowed as it cant be void? Its the script for my second map in a custom story


////////////////////////////
// Run when leaving map
void OnLeave()
{

}