How to pass value to unspecified object using delegate C#

Question

I have a FlowLayoutPanel containing an unspecified number of Labels, when I double click in one of them, a new Form containing a TextBox and a Button will appear, here is the code:

    foreach (Label lb in FlowLayoutPanel1.Controls)

    {

        lb.MouseDoubleClick+=new MouseEventHandler(lb_MouseDoubleClick);

    }

    

    private void lb_MouseDoubleClick(object sender, MouseEventArgs e)

    {

        NewForm form = new NewForm();

        form.ShowDialog();

        ((Label)sender).Text = ...;//I want get text from TextBox of the NewForm here

    }

I want get Text from TextBox of the NewForm and assign Text to the object that invoke the NewForm when user click the Button of the NewForm, I know to use properties or static variable to do this, but I dont know how to use delegate to do this? Please help me,Thanks!