OOC: Sure, note that this item has errata to take out the cleric spells since it is an arcane item. You can let the Searing Light stand since you've already rolled it.
Page 177—Runestaff of Undead Slayer
[Revision]
Substitute deathward with 4th level forceward
(SC 98), disrupting weapon with 6th level
incorporeal nova (SC 121), and
searing light with 3rd level halt undead.
Undeath to death is 6th level
Undeath to Death :: d20srd.org
Detect Undead is 1st level
Detect Undead :: d20srd.org
Halt Undead is 3rd Level
Halt Undead :: d20srd.org