Meta Data in Wavelab Pro Edit Button Greyed Out

I am having trouble editing meta data in wavelab pro. I succeeded in entering all the meta data on an mp3 track but when i opened another track to do the same thing the edit button in meta data tool is greyed out? Do I have to save as an mp3 first? Its currently an aiff file.

Metadata is not supported for AIFF. Convert to WAV first.