Thank You for so fast reply.
I just saw this by this link "http://discussion.bentley.com/cgi-bin/dnewsweb.exe?cmd=article&group=bentley.microstation.v8.mdl&item=14353&utag=" and was very happy that could use already buid-in function.
About deleting, is any buld-in function (like is mdlFile_copy for coping) to delete file or folder?