WPF Drag and Drop

Hello all,
             I am working on WPF from past 5 month.I have a doubt on drag and drop .I am having a list of textblock in a stackpanel (indicating list of person's name).In another grid i have got many images in the shape of  squares. Both these stackpanel and grid are defined inside  same canvas.Now i am supposed to drag and drop the textblock object ,place it only inside any box of the grid from stackpanel.(not anywhere else in the grid,if i place anywhere else object has to disappear.)
  I am facing a problem since i  use mousecapture due to which i am not able to drop using co-ordinates of box, plz help me.I am using VisualStudio 2008 and XAML.

thanks
amchi gele.