diff --git a/lcl/dialogs.pp b/lcl/dialogs.pp
index e82c4ca9c5..2353c63121 100644
--- a/lcl/dialogs.pp
+++ b/lcl/dialogs.pp
@@ -639,8 +639,18 @@ type
 
   { TTaskDialogProgressBar }
 
+const
+  PBST_NORMAL             = $0001;
+  PBST_ERROR              = $0002;
+  PBST_PAUSED             = $0003;
+
+Type
+
   TTaskDialogProgressBar = class(TPersistent)
   private
+    const
+      ProgressBarStateValues: array[TProgressBarState] of Integer = (PBST_NORMAL,PBST_PAUSED,PBST_ERROR);
+    private
     Dlg: TCustomTaskDialog;
     FMarqueeSpeed: Cardinal;
     FMax: Integer;
diff --git a/lcl/include/taskdialog.inc b/lcl/include/taskdialog.inc
index 298963a034..569d510b5c 100644
--- a/lcl/include/taskdialog.inc
+++ b/lcl/include/taskdialog.inc
@@ -120,10 +120,50 @@ end;
 procedure TTaskDialogProgressBar.Initialize;
 //this should be invoked as soon as the dialog has been instatiated (so Dlg.Handle <> 0),
 //so probably in Dlg.DoOnConstructed??
+var
+  Res: LRESULT;
+  Err: Integer;
+  IsMarquee: BOOL;
 begin
   //ToDo:
   //  send TDM_SET_MARQUEE_PROGRESS_BAR to Dlg (differentiates between "normal" and marguee)
   //  send range, position and state to dialog.
+  if (Dlg.Handle <> 0) and (Dlg.Flags * [tfShowProgressBar,tfShowMarqueeProgressBar] <> []) then
+  begin
+    IsMarquee := (tfShowMarqueeProgressBar in Dlg.Flags);
+    writeln('TTaskDialogProgressBar.Initialize: IsMarquee=',IsMarquee);
+    //wParam = 0 (nonMarque) wParam != 0 (Marquee), lParam must be 0
+    //if Both Flags are set, Windows seems to intepret this a Marquee
+    Res := SendMessage(Dlg.Handle, TDM_SET_MARQUEE_PROGRESS_BAR, WPARAM(IsMarquee), 0);  //Result is ignored
+    writeln('TTaskDialogProgressBar.Initialize: TDM_SET_MARQUEE_PROGRESS_BAR: LResult=',PtrInt(Res));
+
+
+    if not IsMarquee then
+    begin
+    //wParam must be 0, lParam = MAKELPARAM(nMinRange, nMaxRange)
+    Res := SendMessage(Dlg.Handle, TDM_SET_PROGRESS_BAR_RANGE, 0, MAKELPARAM(FMin, FMax));   //Zero iindicates failure
+    debugln(['TTaskDialogProgressBar.Initialize: TDM_SET_PROGRESS_BAR_RANGE: LResult=',PtrInt(Res)]);
+    if (Res = 0) then
+    begin
+      Err := GetLastOSError;
+      debugln(['Err=',Err,': ',SysErrorMessage(Err)]);
+    end;
+
+    end//Not IsMarquee
+    else
+    begin //IsMarquee
+    end;
+
+    //wParam = new progress state, lParam must be 0
+    Res := SendMessage(Dlg.Handle, TDM_SET_PROGRESS_BAR_STATE, WPARAM(ProgressBarStateValues[FState]), 0);
+    debugln(['TTaskDialogProgressBar.Initialize: TDM_SET_PROGRESS_BAR_STATE: LResult=',PtrInt(Res)]);  //Zero iindicates failure
+    if (Res = 0) then
+    begin
+      Err := GetLastOSError;
+      debugln(['Err=',Err,': ',SysErrorMessage(Err)]);
+    end;
+
+  end;
 end;
 
 { TTaskDialogRadioButtonItem }
@@ -255,9 +295,9 @@ end;
 
 procedure TCustomTaskDialog.DoOnDialogConstructed;
 begin
-  FProgressBar.Initialize;
   if Assigned(FOnDialogConstructed) then
     FOnDialogConstructed(Self);
+  FProgressBar.Initialize;
 end;
 
 procedure TCustomTaskDialog.DoOnDialogCreated;
diff --git a/lcl/lmessages.pp b/lcl/lmessages.pp
index 4fc095b97a..819fcf1aae 100644
--- a/lcl/lmessages.pp
+++ b/lcl/lmessages.pp
@@ -239,6 +239,24 @@ const
   LM_PASTE             = $0302;
   LM_CLEAR             = $0303;
 
+  // _TASKDIALOG_MESSAGES enum
+  TDM_NAVIGATE_PAGE                   = LM_USER+101;
+  TDM_CLICK_BUTTON                    = LM_USER+102; // wParam = Button ID
+  TDM_SET_MARQUEE_PROGRESS_BAR        = LM_USER+103; // wParam = 0 (nonMarque) wParam != 0 (Marquee)
+  TDM_SET_PROGRESS_BAR_STATE          = LM_USER+104; // wParam = new progress state
+  TDM_SET_PROGRESS_BAR_RANGE          = LM_USER+105; // lParam = MAKELPARAM(nMinRange, nMaxRange)
+  TDM_SET_PROGRESS_BAR_POS            = LM_USER+106; // wParam = new position
+  TDM_SET_PROGRESS_BAR_MARQUEE        = LM_USER+107; // wParam = 0 (stop marquee), wParam != 0 (start marquee), lparam = speed (milliseconds between repaints)
+  TDM_SET_ELEMENT_TEXT                = LM_USER+108; // wParam = element (TASKDIALOG_ELEMENTS), lParam = new element text (LPCWSTR)
+  TDM_CLICK_RADIO_BUTTON              = LM_USER+110; // wParam = Radio Button ID
+  TDM_ENABLE_BUTTON                   = LM_USER+111; // lParam = 0 (disable), lParam != 0 (enable), wParam = Button ID
+  TDM_ENABLE_RADIO_BUTTON             = LM_USER+112; // lParam = 0 (disable), lParam != 0 (enable), wParam = Radio Button ID
+  TDM_CLICK_VERIFICATION              = LM_USER+113; // wParam = 0 (unchecked), 1 (checked), lParam = 1 (set key focus)
+  TDM_UPDATE_ELEMENT_TEXT             = LM_USER+114; // wParam = element (TASKDIALOG_ELEMENTS), lParam = new element text (LPCWSTR)
+  TDM_SET_BUTTON_ELEVATION_REQUIRED_STATE = LM_USER+115; // wParam = Button ID, lParam = 0 (elevation not required), lParam != 0 (elevation required)
+  TDM_UPDATE_ICON                     = LM_USER+116; // wParam = icon element (TASKDIALOG_ICON_ELEMENTS), lParam = new icon (hIcon if TDF_USE_HICON_* was set, PCWSTR otherwise)
+
+
 {$I controlconsts.inc}
 
   //-------------