Add
BN_CLICKED
handlers for all radio buttons to detect state changings. From within the handler, enable or disable dependant controls according to the button states. With your scenario, one function can handle it all:
ON_BN_CLICKED(IDC_RBTN_1, OnBnClickedRadio)
ON_BN_CLICKED(IDC_RBTN_2, OnBnClickedRadio)
ON_BN_CLICKED(IDC_RBTN_3, OnBnClickedRadio)
void CMyDialog::OnBnClickedRadio()
{
CButton *pRadio3 = (CButton*)GetDlgItem(IDC_RBTN_3);
BOOL bEnable = (BST_CHECKED != pRadio3->GetCheck());
GetDlgItem(IDC_SOME_CONTROL)->EnableWindow(bEnable);
m_SomeOtherControl.EnableWindow(bEnable);
}