CS0200: Property or indexer 'System.Web.UI.WebControls.Login.Password' cannot be assigned to -- it is read only

Question

First, I would like to thank any response. You have been big helps in the past. I have used the Login Control (my mistake) for a web application I am developing. I need to pre-populate the Username and Password after the first visit to the page. I create cookies on the first visit on the client's machine. The next visitI can populate the Username but the password will not populate. I receive the error "CS0200: Property or indexer 'System.Web.UI.WebControls.Login.Password' cannot be assigned to -- it is read only". Is there a property that I can change or How can I populate this field? I listed the code that provides this error below. THANKS!

//Populate the password

HttpCookie lnfoPW = Request.Cookies["PW"];

lgin.Password = InfoPW.Value.ToString();