help finding a buff's index value?

[Vardelm]

I'm trying to create a function where I can give the name of a buff and the function will return the value of the index for that buff. Here's what I have so far, but it isn't working.

function GetBuffIndex(thisBuff)
  local counter = 1
  while (UnitBuff("player", counter)) do
    if (string.find(UnitBuff("player", counter), thisBuff)) then
      local buffIndex = counter;
    end
    counter = counter + 1
  end
  return buffIndex
end

Any suggestions on how to get this working? I've tried a bunch of small changes without luck so far. Maybe someone even has a function out there that does this already....?????