Search for files with certain number of @Keywords

[pajaro]

I am trying to search for files with just one @Keyword assigned. Similarly, it would be useful for me to search for files with just two, three... @Keywords. Can this be done? So far I have been able to list files without any @Keyword (using this formula: "@All" NOT ("@Category[@Keywords]")). I search the forum and the help file but did not find anything.

Thanks,

Pavel.