Add this to the CheckAllFields() function:

if(!CheckFileUpload(f.Fld_AttachControl,'Please browse and select a file to attach.')) hasErrors = true;



New function for the Attach Control:

function CheckFileUpload(field, msg) {
	if (field.value == "") {
            field.className = "error"
            errorMsgs += msg + "\n\r"
            field.focus();
            return false;
        }
        field.className = "";
        return true;
}