The IsDlgButtonChecked function determines whether a button control has a check mark next to it or whether a three-state button control is grayed, checked, or neither.
UINT IsDlgButtonChecked(
| HWND hDlg, | // handle of dialog box | 
| int nIDButton | // button identifier | 
| ); | 
The return value from a button created with the BS_AUTOCHECKBOX, BS_AUTORADIOBUTTON, BS_AUTO3STATE, BS_CHECKBOX, BS_RADIOBUTTON, or BS_3STATE style can be one of the following:
| Value | Meaning | 
| BST_CHECKED | Button is checked. | 
| BST_INDETERMINATE | Button is grayed, indicating an indeterminate state (applies only if the button has the BS_3STATE or BS_AUTO3STATE style). | 
| BST_UNCHECKED | Button is unchecked | 
If the button has any other style, the return value is zero.
The IsDlgButtonChecked function sends a BM_GETCHECK message to the specified button control.