In my test run, I was using a column of first names in workbook A to
check and flag their
presence in workbook B, The code given to me by Marcus here worked
fine. No problem at all.
..
When I switched to the real problem by replacing my columns of data
with numbers
with leading zeroes, the columns being already formatted as text, the
program did not find Matches.
..
In both workbooks columns of data, cells have an automatic Excel
comment that says :
"The number in this cell is formatted as text or preceded by an
apostrophe".
..
What am I missing here ?
Is there a special care to be taken when using numbers with leading
zeroes in a cell formatted as text ?
Here is the code :

Sub FlagMatchingRecords()
Dim RngCell As Range
Dim IsMatch() As Variant
Dim res As Variant
Dim lw As Long
Dim lr As Long
Dim X As Range
Dim wb As Workbook
Dim ws As Worksheet
lr = Range("B" & Rows.Count).End(xlUp).Row
Set wb = Workbooks("B.xls")
Set ws = wb.Sheets("Sheet1")
IsMatch() = Range("B1:B" & lr).Value
lw = ws.Range("A" & Rows.Count).End(xlUp).Row


Set X = ws.Range("A1:A" & lw)
For Each RngCell In X
MsgBox RngCell.Value
res = Application.Match(RngCell.Value, IsMatch, 0)
If IsError(res) Then
'No Match
Else ' Match
RngCell.Interior.Color = vbYellow
End If
Next RngCell
End Sub

Help appreciated,

J.P.