The problem has been solved.

The corrected Hal code looks as follows:-

// VER: 5.4 080912
// UST: 23.09.2008 (update)
// VER: 5.3 071214
// UST: 10.01.2008


global
procedure DoRunCMForm(record RcVc Dummyr,record RcVc RepSpec)
begin

    string 30 formcode;
    boolean testf;

    formcode = "INVOICE";

    LogText(0,"Before OpenForm 0");
   
//    FormLabelGrid(1,1,1,1);
    LogText(0,"Before OpenForm 1");
    testf = (OpenForm(formcode)==true);

CloseForm;
    LogText(0,"After OpenForm: " & testf);

return;
end;


global
procedure RunCMForm(record RcVc RepSpec)
BEGIN
boolean tmpf;


tmpf = PrintDocument(RepSpec,"RunCMForm",false);

LBH_StockMovLabelForm:;

RETURN;
END;




So the procedure with openform() in it has to be called via PrintDocument()

tmpf = PrintDocument(RepSpec,"RunCMForm",false);