Try something like this :
select case extension
case ".jpg", ".jpeg", ".gif" '##Image File extensions
allowFile=true
ImageFileType=true
case ".bin", ".hex" '##Image File extensions
allowFile=true
ImageFileType=false
case ".txt", ".doc", ".pdf", ".bin", ".hex" '##Downloadable file extensions
allowFile=true
case else
allowFile=false
end select
I've never used this MOD, but that might help.