extern  "C"  int __declspec(dllexport) GetStandartProductID(int NonStandartProductID, int& ColorID, unsigned char& modificator);
...
int __declspec(dllexport) GetStandartProductID(int NonStandartProductID, int& ColorID, unsigned char& modificator){
   return(NonStandartProductID+ColorID+(int)modificator);
}

function _GetStandartProductID(NonStandartProductID:Integer;var ColorID:Integer;var Modifikator:Char):Integer; cdecl;external'Project1.dll';
...
procedure TForm1.Button1Click(Sender: TObject);
var R,a,b:Integer; c:Char;
begin
   a :=  100 ;
   b :=  20 ;
   c := # 3 ;
   R := _GetStandartProductID(a,b,c);
   Application.MessageBox(PChar(IntToStr(R)),'', 0 );
end;