Procedure HexToLongInt(Hex:String; Var Decimal:LongInt; Var Code:Integer);

    The string Hex may be any  length.   The value is returned in Decimal
    unless an illegal  character  is  detected  in  Hex.   If  an illegal
    character is detected,  Code  indicates  the  position of this error.
    If  Code  >  0   then   Decimal   is   undefined.    If   Code   =  0
    then  no  error  occurred.   Hex   may  be  in  Pascal  or  Assembler
    style, but not  BASIC  style.   If  Hex  is  too  long,  Code  is set
    to 255.

    Examples

    If Hex is '&HB' then Code = 1.
    If Hex is '$A' then Code = 0 and Decimal = 10.
    If Hex is 'b' then Code = 0 and Decimal = 11.
    If Hex is '4h' then Code = 0 and Decimal = 4.