alllist = List();
alllist = {"png","PNG","JPEG","jpeg","JPG","jpg","GIF","gif","BMP","bmp"};
var = "";
if(input.Attachment != null)
{
	ext = input.Attachment.toList(".").get(input.Attachment.toList(".").size() - 1);
}
rpl = replaceAll(ext," border = \"0\"></img>","");
var = rpl.replaceAll("\"","");
if(!alllist.contains(var) && var != "")
{
	alert "This file type is not accepted. Only PNG,JPG,JPEG,BMP file formats are allowed";
}