audio_form object
This method will set the checked or unchecked state of a checkbox.
bool set_checkbox_mark(int control_id, bool checked)
Parameters:
control_id
The ID of the control you wish to change.
checked
A boolean value indicating whether the control should be checked. A value of true means the checkbox will be checked, while a value of false means the checkbox will not be checked.
Return value:
true on success, false on failure.
Remarks:
None.
Example:

    // Make a simple form with a checkbox that changes state after its creation.

    #include "form.bgt"

    audio_form form;

    void main()
    {
    form.create_window("Example Form", true);
    int checkbox=form.create_checkbox("&Change me", true);
    form.set_checkbox_mark(checkbox, false);
    int ok=form.create_button("OK");
    while(true)
    {
    form.monitor();
    wait(5);
    if(form.is_pressed(ok))
    {
    exit();
    }
    if((key_down(KEY_LMENU))&&(key_pressed(KEY_F4)))
    {
    exit();
    }
    }
    }