Dark Sim script question

[WholeGrainOats]

Any chance anybody knows how i can cause my dark simulacrum to cast when a players casting or channeling a certain spell? for example, ive tried doing this

/run if UnitCastingInfo("target","Regrowth") and IsUsableSpall("Dark Simulacrum") then CastSpellByName("Dark Simulacrum") end;

/run if UnitCastingInfo("target","Cyclone") and IsUsableSpall("Dark Simulacrum") then CastSpellByName("Dark Simulacrum") end;

But it isnt seeming to work, Any ideas/known methods to do this in one string?