Upload de Imagem

Como eu faço para mudar o nome do arquivo antes de salvar a imagem ?

SaveFiles()

function SaveFiles
Dim Upload, fileName, fileSize, ks, i, fileKey

Set Upload = New FreeASPUpload

Upload.Save(uploadsDirVar)

If Err.Number <> 0 then Exit function

SaveFiles = ""
ks = Upload.UploadedFiles.keys

if (UBound(ks) <> -1) then
for each fileKey in Upload.UploadedFiles.keys
SaveFiles = SaveFiles & Upload.UploadedFiles(fileKey).FileName
next
end if