The event is going to firer anytime you address the textbox, even during the
load of the form. It could be a case that you must load a textbox during the
Form_Load  with data.

In any case, you must set a flag at Form_Load like bFormLoad = true and set
bFormLoad = false after the Form_Load.

Then when the Textbox_Changed event firers doing the Form_Load when
addressing the Textbox, if bFormLoad = true, then you bypass the code in the
event. Then after Form_Load when you set bFormLoad = false, you are safe to
execute the code in the event, because the user entered data in the Textbox,
after the Form_Load.