Harold,
How is Maud?  I am sorry, I just could not resist.
Here is a soloution to your quandry.
I a column that is free you are going to write this.  This is assuming
that the column you are interested in is A.
=IF(ISERROR(Search("details.xls",A1,1))=True,0,1)  Here is how this
reads.  If a1 is serached and it can not find details.xls in the cell
it will return a 0, if it can then it will return a 1.  then all you
have to do is find the zeros.
Hope this helps,
Jay

There's nothing built into excel that allows you to look at the formula.

You could use a user defined function, though:

Function GetFormula(Rng As Range)
   Dim myFormula As String
   GetFormula = ""
   With Rng.Cells(1)
       If .HasFormula Then
           If Application.ReferenceStyle = xlA1 Then
               myFormula = .Formula
           Else
               myFormula = .FormulaR1C1
           End If
           If .HasArray Then
               GetFormula = "{=" & Mid(myFormula, 2, Len(myFormula)) & "}"
           Else
               GetFormula = myFormula
           End If
       End If
   End With
End Function

If you're new to macros, you may want to read David McRitchie's intro at:
http://www.mvps.org/dmcritchie/excel/getstarted.htm

Short course:

Open your workbook.
Hit alt-f11 to get to the VBE (where macros/UDF's live)
hit ctrl-R to view the project explorer
Find your workbook.
should look like:   VBAProject (yourfilename.xls)  

right click on the project name
Insert, then Module
You should see the code window pop up on the right hand side

Paste the code in there.

Now go back to excel.
Into a test cell and type:
=getformula(a1)

After you have it working, you can insert a new column and return the formula
from each of the adjacent cells.