yes
You can use the panel attribute ATTR_PANEL_FIRST_CTRL to obtain the first control on a panel, and then the control attribute ATTR_NEXT_CTRL to find all other controls:
GetPanelAttribute ( panel_handle, ATTR_PANEL_FIRST_CTRL, &control_id );
while ( control_id > 0 )
GetCtrlAttribute ( panel_handle, control_id, ATTR_NEXT_CTRL, &control_id );