Here's how to check, uncheck, enable, and disable a checkbox in MFC:
CButton* pBtn = (CButton*) GetDlgItem(IDC_SETUP_AM);
pBtn->SetCheck(0);// uncheck it
CButton* pBtn = (CButton*) GetDlgItem(IDC_SETUP_AM);
pBtn->SetCheck(1);// check it
CButton* pBtn = (CButton*) GetDlgItem(IDC_SETUP_AM);
pBtn->EnableWindow(0);// disable it
CButton* pBtn = (CButton*) GetDlgItem(IDC_SETUP_AM);
pBtn->EnableWindow(1);// enable it
Larry A. Mills, Sr.