Problem with forms and their names

Hi, I’m having trouble with my application. I can’t seem to get forms to communicate together. I’ve started off with a simple test like this:

Code:

Form2.Label1.Text = "hello"

Here’s the code that creates my forms from my main menu class:
(I should explain that my main menu form has a textbox and a button, when the user types something in and clicks the button a new form is created.)

Code:

Public Class MainMenuClass
    Dim mynum As String
    Private frm_MainMenu As MainMenuForm
    Public TestArray As New ArrayList
    Private c_NewForm As NewFormClass

    Public Sub New(ByVal frm As MainMenuForm)
        frm_MainMenu = frm
    End Sub

    Public Sub createNewForm(ByVal Uinput As String)
        c_NewForm = New NewFormClass(Uinput, Me)
        TestArray.Add(c_NewForm)
        c_NewForm.Display()
        
    End Sub

If 2 new forms are created and the user input the names “joe” and “bob” for them, that should be one newform called joe and one called bob. And each has there own newform class. From each of the new forms the user can type into a textbox and click a button to see if there is a form open with that name. I have tried many things and I cant figure out how to pass the name from the textbox to a string to be used like this:

Code:

Dim TestString as String = textbox.1.text
TestString.Label1.Text = "hello"

Any help would be great, thanks.