... none of it's working now.

Can you describe what isn't "working now"... what do you see happen (or
not
happen)?

Here is what I think your post asked for (if this is incorrect, then you
will need to post a more detailed description, with examples perhaps, of
what you actually want). If an entry in the range of AC8 through to the
end
of Row 8 contains an a single character entry, then you want to
concatenate
the contents of the cell in the same column, but in Row 3, with other
with
the other cells from Row 3 whose 8th row counterparts also contain a
single
character entries in Row 3 (starting at Column "AC"). Unless I have
missed
something, that is what the code I posted (the Worksheet Change event
code,
not the function one) does.

Yes, thanks, it's going all right now. But... the formula I typed in
X8 has disappeared, there's only the concatenated text. And i want to
copy it down to 9 rows below. Will I have to just type it in 9 more
times?

You **do** want to copy it down.... okay, I could adjust the range to do
that, but I'm thinking maybe a User Defined Function (UDF) is a better
choice because it will be more flexible for how you want this functionality
to be implemented. Give this UDF a try and see if it works for you
(remember, the UDF code goes into a Module... key in Alt+F11 from the
worksheet, then Insert/Module from the menu bar)...

Function BigConcatenate(RangeToTest As Range, ConcatRow As Long) As String
Dim C As Range
For Each C In RangeToTest
If Len(C.Value) = 1 Then
BigConcatenate = BigConcatenate & Cells(ConcatRow, C.Column).Value
End If
Next
End Function

The BigConcatenate UDF requires 2 arguments... the range you are going to
test for having a single character and the row number (not a range, but a
number) containing the text you want to concatenate. This is the formula you
would put in X8...

=BigConcatenate(AC8:IV8,3)

This formula can be copied down.

Rick