Call Control properties From MDI

In visual basic 6 i can call controls properties from forms, modules, etc
like this
Sub UserName() ' this is my module
FrmData.Txtuser_name.Text = "Jimmy"
End Sub

FrmData is a form with one textbox called Txtuser_name and i set it's text
as Jimmy

How can i do it in visual basic .net? i tried to do it from a module but i
does not work.
Thanks and sorry for my english