Send button id from one form to another in windows app

Question

Hi,

I have created one application where i am using two form - 1) planform and 2) statusform

 and 3rd form i have created to send mail, I have done coding - 

public void sendmailbtn_Click(object sender, EventArgs e)

        {

            planform obj = new planform();

            statusform obj1 = new statusform(); 

            MailMessage mail = new MailMessage();

           

            mail.To.Add(tobox.Text);

            mail.From = new MailAddress(frombox.Text);

    mail.Subject = DateTime.Now.ToShortDateString() + "-Planned Task Register (PTR)"; // subject

            mail.Body = bodyboxarea.Text;

            mail.CC.Add(new MailAddress(ccbox.Text));

            mail.IsBodyHtml = true;           

            System.Net.Mail.Attachment attachment;

            attachment = new System.Net.Mail.Attachment(filebox.Text);

            mail.Attachments.Add(attachment);

            

            SmtpClient smtp = new SmtpClient();

            smtp.Host = "smtp.gmail.com";

            smtp.Credentials = new System.Net.NetworkCredential("gmailid", "password");

            smtp.EnableSsl = true;

            smtp.Send(mail);

            this.Hide();           

            MessageBox.Show("Mail sent");

        }

it is working fine, currently "subject" will be same for both plan and status but i want subject line should change when i ll click on status form

it should be like -

    mail.Subject = DateTime.Now.ToShortDateString() + "-StatusTask Register (PTR)"; // subject

   

            for this i have created global variable but still i did'nt get...

    how i ll do that??