Form open? and if=true, close. C#

///How to check if form is open, and if its already open, close it:
///CCAPI EXAMPLE:
///(C#)
using System
using System.IO;

if (radioTMAPI.Checked)
            {
                this.PS3.ChangeAPI(SelectAPI.TargetManager);
            }
            else
            {
                if (!File.Exists(Directory.GetCurrentDirectory() + "/CCAPI.DLL"))
                {
                    CCAPIno CCno = new CCAPIno();
                    ipaddress.Enabled = false;
                    this.radioTMAPI.Checked = true;
                    CCno.Show();
                }
                else
                {
                    //   this.rbtnTMAPI.Checked = true;
                }
            }

/////////////////////////////////OTHER FORM -- The Error message saying CCAPI Doesn't exist/////////////////////////////////

public CCAPIno()
        {
            InitializeComponent();
            this.FormClosing += this.CCAPIno_Closing;
        }
        static bool s_bFormOpened = false;  // static variable that indicate the form has opened or not
        private void CCAPIno_Load(object sender, EventArgs e)
        {
            {//if one form was opened now, the current form will be closed
                if (!s_bFormOpened)
                    s_bFormOpened = true;
                else
                    this.Dispose();
            }
        }
        private void CCAPIno_Closing(object sender, FormClosingEventArgs e)
        {//restored the state
            if (s_bFormOpened)
                s_bFormOpened = false;
        }
    }