VB.net WPF Form location

I'm very new to vb.net, so please bear with me.

I'm busy designing a WPF form in VB.net need help with the following: I have a checkbox that, if checked, needs to get the on screen location of the form and save that location.

I need to let the form start up in the saved location if the checkbox was ticked, if it wasn't the form needs to start in the default position on the screen.

Please help