I believe this will work - I used a custom function rather than Sarah's slicker way of using arrays. It's a little long hand, but so long as you're not doing this for 20 thousand cells at once, it should be manageable. Open up the Visual Basic Editor (Alt F11), insert Module, and paste the following code. Then just reference this function as if it were any other function. (e.g., =numerology("far") = 6118)
Function numerology(word)
letters = Array("a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", _
"o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z")
For ltr = 1 To Len(word)
For indx = 1 To 26
If LCase(Mid(word, ltr, 1)) = letters(indx - 1) Then
numerology = numerology & indx
Exit For
End If
Next indx
Next ltr
numerology = Val(numerology)
End Function