>No, it didn't work. I tried all possible combinations yesterday I could think of and was not able to make it.

I think you may be expecting to be able to embed too much code into the aspx (not saying it's not possible, but that I would try a different approach). I would just create a method in the code-behind file that accepts an object parameter and returns a string. Then from within the aspx file, call the method and pass in the eval:

// In ASPX file, something like this:
<%= this.FormatField(Eval("Field")) %>

In your codebehind just convert it back into it's original type or to a string and return back whatever you'd like, ex. ToString()