Visual C++ :: How To Pass Value From One Form To Another

i am trying to create a form app with multiple forms. there is a form i'm using as "search". i want to take the value of the textbox in search-form and pass it to another form which shows the result of the search. i've tried to include search-form.h in the form of the result but it returns an error.

Code:

String ^ key;
key = searchbox->Text;
std::string ks = marshal_as<std::string>(key);
ks=ks+".bin";
ifstream sfile(ks);
if (sfile) {
PatInfo ^ form = gcnew PatInfo;
form->ShowDialog();
} else {
MessageBox::Show( "Please try again.");
}

to conclude, i want the form PatInfo to open an receive the "ks" var.