Change label text of MDI child form

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Basic

I have one child Form (Form2) in a MDI project with one label and one button control.
Form2 also having a public Sub ChangeText(). When run this SUB changes the Label text.
On clicking the Button one Modal Form will pop up. This modal Form also having a Button.
On clicking the Modal Form Button, Modal Form will Close and Label in Form2 Text Changed.

But this is not happening. Note that Form2 is a MDI Child form.

Any one please suggest how do I do this.

Thanks a lot. I have got the mistake I was making.
No need to suggest any. Thanks.

What I have tried:

I have created a property in the MDI Parent Form (Form1). When property value changes it triggered an event. I added AddHandler (Property value changed event), addressOf the public Sub of Form2. Modal Form Button changes the Form1 Property Value, which raises the event and event handler runs the public Sub of Form2. Actually the sub changes the Text of the label but it is not shown. Since the label is auto size, its width changes.