For my macro'd abilities (like my one-button DPS spam), I use the following:

Code:
/console Sound_EnableSFX 0
<do some stuff that might generate errors here>
/script UIErrorFrame:Clear() 
/console Sound_EnableSFX 1
That actually flickers the message briefly, but it's so fast I don't notice. There are macro commands to disable displaying the frame completely so you don't even get the flicker, which might be a bit nicer if macro length is not an issue for you.