Create a member variable for the tab control.

In each of the button handlers, call SetCurPos for the tab control.

For example, in the first button handler:
Code:
m_TabCtrl.SetCurPos( 0 );  // zero based index sets the first tab
..the second button handler:
Code:
m_TabCtrl.SetCurPos( 1 );  // zero based index sets the first tab