in the property tab of the another form2 you must change the modifier of the datagridview to public, than you must add an object of type form2 to form1:
or maybe from the main class you must add the from2 object an use it
(form2 f = new form() use f.show() and f.hide() or anything)
class form1:form
{
form2 F = new form2();
"in the event" textbox.text_changed(...)
{
...use you search code using F.datagridview2. ...( datagridview2 must be public...)
}
}