function alpha_check(str,ext){  // remove all other chracters
var str;var ext;var chtr;
allowable="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"+ext;
newstr="";
    for(p=0;p<str.length; p++){
        chtr=str.charAt(p);
        if(allowable.indexOf(chtr)!=-1){
        newstr=newstr+chtr;
        }
    }
return newstr;
}