.... Is Inaccessible due to its protection level

Hi there,
I am currently doing a C# project for my degree in the UK. i am trying to 'copy' infomation over from one form to the other by setting the text property of one equal to the text property of the other, you can see this below.

frmBill BillForm = new frmBill();

public void btnSeeBill_Click(object sender, EventArgs e)
        {
            BillForm.lblName.Text = txtName.Text;   
        }

I cannot see why this code will not work as the error i get is:  'C_sharp_DOT_NET_Project.frmBill.lblName' is inaccessible due to its protection level

please can you help me with this as i have to hand this in soon.

Thanks in advance for your help :-)
Darren Rutter