For anyone it may help, here is the macro. It cycles through the raid marks and plays a sound when it finds the target:
/cleartarget
/tar lunarlight
/run local r,T,t,a=SMRI,nil,“target”,{8,7,1,2,3,4} if not r then r=1 end if UnitExists(t)then T=t end if T then if GetRaidTargetIndex(T)==nil then SetRaidTarget(T,a[r]) PlaySound(12867,“master”) r=r%#a+1 end end SMRI=r