Fastest way to check if a number is divisible by three?

Hi experts,

What's the best way to tell if a number is evenly divisible by three?  For instance, I have been doing it like this:

For i = 1 to 10,000
  if i / 3 = i \ 3 then
    'do something
  end if
next i

That's quite neat... but I don't think it's very fast because the computer hates the / symbol.  I could do it using the ROUND function as well, but that is also slow.  I suppose I could also do:
blnfirstmatch = true
blnsecondmatch = false

For i = 1 to 10,000
  if blnFirstMatch = true then
    blnFirstMatch = false
    blnSecondMatch = true
  elseif blnSecondMatch = true then
    blnSecondMatch = false
  else
    blnFirstMatch = true
   'do something
  end if
next i

There are probably other ways too.  If any experts can let me know what is definitely the fastest way, I would be very very grateful.

Thank you,

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