[JRD!]

If you want just "Create a desktop icon" in the Ready Memo with your personal IconCB:

[Tasks]
//Name: "desktopicon"; Description: "{cm:CreateDesktopIcon}"; GroupDescription: "{cm:Icons}";
Name: "groupicon"  ; Description: "{cm:CreateGroupIcon}";   GroupDescription: "{cm:Icons}";

[CustomMessages]
Icons=Icons:
CreateDesktopIcon=Create a desktop icon
CreateGroupIcon=Create a startmenu icon

[#Code]
var
  IconCB: TNewCheckBox;

function UpdateReadyMemo(Space, NewLine, MemoUserInfoInfo, MemoDirInfo, MemoTypeInfo,
  MemoComponentsInfo, MemoGroupInfo, MemoTasksInfo: String): String;
var
  S1, S2: String;
begin
  S1 := '';
  S2 := '';
  S1 := S1 + MemoDirInfo + NewLine + NewLine;
  if IconCB.Checked then
  S2 := #32#32#32#32#32#32#32#32#32+CustomMessage('CreateDesktopIcon');
  S1 := S1 + MemoTasksInfo + NewLine + S2 + NewLine;
  Result := S1;
end;

If you want show your personal IconCB in the memo add this code:

[#Code]
Procedure CurPageChanged(CurPageID: Integer);
begin
  if CurPageID = wpReady then IconCB.Show else IconCB.Hide;
end;

For IconCB creation:

Procedure InitializeWizard();
begin
  IconCB := TNewCheckBox.Create(WizardForm);
  with IconCB do
  begin
    Parent := WizardForm.ReadyMemo;
    SetBounds(25,150,150,15);
    Caption:=CustomMessage('CreateDesktopIcon');
    Checked:=True;
  end;
end;

I have not quite understood your request ...