How to check double byte (Simple Way)

//TEmpVar ==> Text
//ASCIIText ==> Integer
TempVar := 'Special Characters (Kanji,Chinese,etc)';
ASCIIText := TempVar[1];
IF ((ASCIIText > 128 ) AND (ASCIIText < 160)) OR
   ((ASCIIText > 223 ) AND (ASCIIText < 240))
THEN
  MESSAGE('double byte');