Selects (adds a check mark to) a given radio button in a group and clears (removes a check mark from) all other radio buttons in the group.
void CheckRadioButton(
   int nIDFirstButton,
   int nIDLastButton,
   int nIDCheckButton 
);
Parameters
- nIDFirstButton 
 Specifies the integer identifier of the first radio button in the group.
- nIDLastButton 
 Specifies the integer identifier of the last radio button in the group.
- nIDCheckButton 
 Specifies the integer identifier of the radio button to be checked.
Remarks
The CheckRadioButton function sends a BM_SETCHECK message to the specified radio button.
Example
// Of the 4 radio buttons, selects radio button 3.
void CMyDlg::OnMarkRadio() 
{
   CheckRadioButton(IDC_RADIO1, IDC_RADIO4, IDC_RADIO3);   
}
Requirements
Header: afxwin.h