I have a doubt in MS Excel?

If I have 500 client's Name & addresses with business details in sheet1 and 1000 Client's Name & addresses in another sheet2, How do I check whether the sheet 2 has included any / All of the 500 clients?

Write a small macro.
assuming you have column A in sheet1 with the client's name and data starts from A2; similarly, for same setup in sheet2.
In View menu, click tool bar then Form, a tool bar will appear. Select button to create a button in sheet1. In the Assign Macro screen, click new. In between the Sub and End sub, paste the following macro

Dim lastrow As Integer, c As Object, mrec As String
lastrow = Cells(Rows.Count, 1).End(xlUp).Row
Set sht = Worksheets("sheet2")
For Each cell In Range("A2:A" & lastrow)
Set c = sht.Columns(1).Find(cell, lookat:=xlPart)
If Not c Is Nothing Then
If c = cell Then
mrec = c.Address
cell.ClearComments: cell.AddComment "row" & c.Row
Do
Set c = sht.Columns(1).FindNext(c)
If Not c Is Nothing And mrec <> c.Address And c = cell Then
Text = cell.Comment.Text
cell.ClearComments
cell.AddComment Text & "/row" & c.Row
End If
Loop While mrec <> c.Address
End If
End If
Next

Now, if one clicks the button, it will add a red triangle on the top righthand corner, indicating that it has found identical name in sheet2. The comment will indicate identical name in which row.

try URL, hope it will be helpful

http://en.allexperts.com/q/Excel-1059/co...

Please use the vlookup formula to determine it.