You don't say what version of Visual COBOL for .NET you're using. With recent dialects, it would be something like the following:

method-id. limparTextBoxes.
procedure division using by value controles as type Control.ControlCollection.
    declare ctrl as type Control
    perform varying ctrl through controles
        if ctrl instance of type TextBox
            declare tb as type TextBox = ctrl as type TextBox
            set tb::Text to string::Empty
        end-if
    end-perform
end method limparTextBoxes.

I haven't tried that. I didn't use all the most recent syntax enhancements, since I don't know which ones your version of Visual COBOL supports.

Thank you for your help. Your example works to forms without containers and in this post I forgot to specify this. I got as follows, do not know if it's the best way, but it works.

method-id tsBtnLimpa_Click final private.

procedure division using by value sender as object e as type System.EventArgs.

   invoke limpaCampos()

end method.

method-id. limpaCampos public.

    *> le os controles dentro do (container) panel principal        

    perform varying myobj as type Control thru self::panel::Controls

         *> limpa os textboxs dentro do panel principal

         if myobj instance of type TextBox

            declare tb as type TextBox = myobj as type TextBox

            set tb::Text to string::Empty

         end-if  

         *> limpa o checkBox dentro do panel principal

         if myobj instance of type CheckBox

            declare tb as type CheckBox = myobj as type CheckBox

            set tb::Checked to false

         end-if            

         *> limpa o maskedTextBox dentro do panel principal

         if myobj instance of type MaskedTextBox

            declare tb as type MaskedTextBox = myobj as type MaskedTextBox

            set tb::Text to string::Empty

         end-if          

         if myobj instance of type GroupBox

            *> limpa os controles dentro dos containers GroupBoxs

            perform varying ctrl as type Control thru myobj as type GroupBox::Controls

                   *> limpa textboxs

                   if ctrl instance of type TextBox

                      declare tb as type TextBox = ctrl as type TextBox

                      set tb::Text to string::Empty

                   end-if

                   *> limpa maskedTextBoxs

                   if ctrl instance of type MaskedTextBox

                      declare tb as type MaskedTextBox = ctrl as type MaskedTextBox

                      set tb::Text to string::Empty

                   end-if  

            end-perform

         end-if  

    end-perform

end method.