That's a closure so butt2 and butt3 are in scope, if you assign them before setting butt1's event handler you can just refer to them by name, i.e.
butt1 = (ImageButton) findViewById(R.id.Butt1);
butt2 = (ImageButton) findViewById(R.id.Butt2);
butt1.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
butt2.Text = "whatever";
}
});