Hai try this

 
Dim datawk As Workbook
Dim last_row, this_last_row As Integer
Dim hold() As Variant
Set datawk = Workbooks.Open("C:\Documents and Settings\User\My Documents\sample.xls")
last_row = Workbooks("sample").Sheets(1).Cells(Rows.Count, 3).End(xlUp).Row
Workbooks("sample").Sheets(1).Activate
ReDim hold(1 To last_row - 1) As Variant
For i = 1 To last_row - 1
    hold(i) = Cells(i + 1, 3).Value
Next i
this_last_row = ThisWorkbook.Sheets(1).Cells(Rows.Count, 3).End(xlUp).Row - 1
ThisWorkbook.Sheets(1).Activate
For ii = 1 To this_last_row
    chk = Cells(ii + 1, 3).Value
    
    For chk_val = 1 To last_row - 1
        
        If chk = hold(chk_val) Then
        
            Cells(ii + 1, 3).Interior.Color = vbRed
        
        End If
    
    Next chk_val
Next ii

Workbooks("sample").Close