This is the code section from inno setup.My intention is to make two Checkbox where at a time one is being selected. But this code return error when first checkbox is clicked. section: [Code] var Box2,CheckBox: TCheckBox; //Yes global variable. procedure CheckBoxOnClick(Sender: TObject); begin if Checkbox.Checked then //generate error BEGIN CheckBox.State := cbUnchecked; Box2.State := cbChecked; END else BEGIN CheckBox.State := cbChecked; Box2.State := cbUnchecked; END; end; procedure Box2OnClick(Sender: TObject); begin if Box2.Checked then //generate error BEGIN CheckBox.State := cbChecked; Box2.State := cbUnchecked; END else BEGIN CheckBox.State := cbUnchecked; Box2.State := cbChecked; END; end; procedure CreateTheWizardPages; var Page: TWizardPage; begin Page := CreateCustomPage(wpWelcome, 'Support Us', 'If you like this package ,then please support us.'); CheckBox := TCheckBox.Create(Page); CheckBox.Top :=ScaleY(8)+ScaleX(50); CheckBox.Width := Page.SurfaceWidth; CheckBox.Height := ScaleY(17); CheckBox.Caption := 'Do this'; CheckBox.Checked := True; CheckBox.OnClick := @CheckBoxOnClick; CheckBox.Parent := Page.Surface; Box2 := TCheckBox.Create(Page); Box2.Top :=ScaleY(8)+ScaleX(70); Box2.Width := Page.SurfaceWidth; Box2.Height := ScaleY(17); Box2.Caption := 'No,Thanks.'; Box2.Checked := False; Box2.OnClick := @Box2OnClick; { } Box2.Parent := Page.Surface; end; procedure InitializeWizard(); begin { Custom wizard pages } CreateTheWizardPages; end; Returns an error on firstbox click named: Access violation at address 00444400. Write of address 011ABFF8. Please tell me where to change..