NAV 5.0 - SP1 Barcode problem

Hope someone can help me with the following.

I have a problem with calling the function EncodeBarde128. When the function is called, the minimum of parameters is used

Who is familiar with the barcode printing and can tell me if I should add something to the source expression.

Source expression is: EncodeBarcode128

Code is:

StartChar:=‘š’;
StopChar:=‘œ’;
Checksum:=104;

FOR i:=1 TO STRLEN(pText) DO BEGIN
currentchar:=pText[i];
Checksum := Checksum +(i*(currentchar-32));
END;
ChecksumChar:= Checksum MOD 103;
ChecksumChar := ChecksumChar +32;
//convert SPACE to ALT+0128
pText:=CONVERTSTR(pText,’ ',‘€’);

RetVal:=STRSUBSTNO(’%1%2%3%4’,StartChar,pText,ChecksumChar,StopChar);
EXIT(RetVal);