Textbox to SecureString?

Hello,

I'm creating a replacement for Microsoft's iisadmpwd password change facility which allows our users to change their domain passwords when not on a domain joined PC.

I have 5 textboxes:

Domain
User
Old Password
New Password
New Password2

I am converting the contents of the password text boxes to secure strings before sending to AD, but I'd prefer that when users enter data into the text boxes it's appended to a secure string automatically.

I see various solutions for Windows Forms such ashttp://weblogs.asp.net/pglavich/Secure-TextBox-Updated but I cannot find one for Web Forms.

Is there any such control?

Thanks

Karl