This function retrieves text of the OK code text field.
SapGui.bdh
SapGuiGetOkCode( ) : string;
transaction TMain
  var
    sText : string;
    sConnID : string;
  begin// Connecting to SAP
    sConnID := SapGuiOpenConnection(" /SAP_CODEPAGE=1100 /FULLMENU 10.5.2.132 0 /3");
    SapGuiSetActiveConnection(sConnID);
    SapGuiSetActiveSession("ses[0]");
    // SAP
    SapGuiSetActiveWindow("wnd[0]", "SAP", SAPGUI_MATCH_ExactNoCase);
    SapGuiWindowAction(SAPGUI_WND_MAXIMIZE);
    SapGuiLogon("ddic", "*******", "000", "");
    sText := SapGuiGetOkCode();
  end TMain;