Matrix Link Button

Hi,

I have a Matrix which has order doc num in one of the columns. I have set a link button for this column inorder to open the respective order document when the user clicks the link button nect to doc number. Howeverm i'm getting an error saying that no match found.... When i tried the same using docentry insted of doc num everything works perfect. However, i think it is not a good practice to expose the docentry. Is there any way by which I can use Docnum with linkbutton?

Thanks

Ajith