Cross-thread operation not valid (How to access WinForm elements from another module events?)

You need to use the forms dispatcher.

FormContaingTheTextbox.Invoke(new MethodInvoker(delegate(){
    textBox1.Text += " val: " + myval.ToString() + " ";
}));

This makes that code run in the forms thread instead of yours.

Try Using below Code:

this.Invoke(new MethodInvoker(delegate() 
{ 
//Access your controls
}));

hope this helps