2| Hire the mercenary in Twinblade's Camp, bring him to the chapel & sacrifice him at midnight.
3| The easiest way to know it's midnight, is because u pay the mercenary goud every hour. Once your money bag pops up tonen u he's getting meer gold, wait for it to disappear & talk to the man closest to the entrance of the chapel.
4| u know for sure you've got Skorm's Bow when the man says, "Your desire for my evil influence is gratifying. u will go far."
It's seriously as simple as that. Trust me, I've tested this method out several times just to make sure it wasn't some kind of weird game glitch. I don't think it is personally, because whenever I use this method it always works & I get it on the very first try every single time.
{By the way, I play it on the Xbox, so I'm not sure if it'll work the same if u play the PC version.}