GridView: how to hide/show controls based on a value in another cell?

Hi,

I have a GridView with five columns. One of the column renders its content
either as a FileUpload or TextBox - depending on a value in another cell. I
created an EditItemTemplate for the column and placed both controls in it.
The controls' Visible property is initially set to false for both of them.
Based on a value of another field I'd like to be able to set Visible
property to true for one of the controls.
Could someone please let me know the best way of doing this?

Thanks,
Dan