Documented t-sql for file space ?

Hi There

I would like to write sql to check that space used by any given data file in SS2000.

sp_spaceused only returns the total space used by the DB or object in the DB, not for a specific data file.

DBCC SHOWFILESTATS does give me this information , but it is not documented in BOL, i would prefer not to use an undocumented command to ensure future use in later versions. Is DBCC SHOWFILESTATS an undocumented T-SQL command ? If so what documented t-sql command will provide me with this information ?

I could query system table's and work this out , but as mentioned this may not not work in future versions of SS.

Thanx

Dont worry, seems FILEPROPERTY function will do this for me , thanx