Read from one form to another

[cashdeskmac]

I have a button_click event handler with the following code:

string str = lbStaff.SelectedItem.ToString();
getID(ref str);
Form1 fm = new Form1();
fm.txtID.Text = str;

where lbStaff is the name of a listbox, getID is a method which extracts the
ID from a string which includes the ID and full name, txtID is the name of a
textbox in Form1 and Form1 is the name of the main form.

i've been through the debugger, stepping through the event handler and the
output window shows that str = "2", which is the result that I require.
However, the number 2 does not appear in the txtID textbox.

Any suggestions?