Programically open a Combobox

["Ed Welch" <ed_welch inbox net>]

I'm a newbie GTK user. 
I'm trying to make the list part of a combobox drop down programically in GTK 1.2.
First I tried to do it by sending a mouse click event:
  GdkEventButton event;
  event.x_root = m_pointActivate.x;
  event.x_root = m_pointActivate.y;
  gtk_signal_emit (GTK_OBJECT (m_widget), GDK_BUTTON_PRESS, &event);

This had no effect.
Then I tried getting the button part of the combobox and calling gtk_button_clicked:
  GtkWidget *button = GTK_COMBO(m_widget)->button;
  gtk_button_clicked((GtkButton *)button);

Again no effect
If there are any GTK experts out there that can help me, I would greatly appreciate it.
Ed