下面的代码会不会做手脚？

Option Explicit
Sub Found()
Dim NumberOfValues1, NumberOfValues2, NumberOfValues3 As Integer
Dim i, n, o As Long
Dim wb1, wb2 As Workbook
Dim wbsb1, worksheet1, worksheet2 As Worksheet
Dim newExcel As Excel.Application
Set newExcel = CreateObject("Excel.Application")
Dim value1, value2, value3 As String
    
    Set wb1 = Workbooks.Open("C:\anil\commvault\DSM_Master_Full Tapes.xlsx")
    Set wb2 = Workbooks.Open("C:\anil\commvault\DSM_Master_Incremental.xlsx")
    
    
NumberOfValues1 = ThisWorkbook.Sheets("OPEN Media Consolidation").Range("A2").End(xlDown).Row
Set wbsb1 = ThisWorkbook.Sheets("OPEN Media Consolidation")
Application.Calculation = xlCalculationManual
Application.ScreenUpdating = False
For i = 2 To NumberOfValues1
          value1 = wbsb1.Range("C" & i).Value
           For Each worksheet1 In wb1.Worksheets
                NumberOfValues2 = worksheet1.Range("A1").End(xlDown).Row
                 For n = 1 To NumberOfValues2
                  value2 = worksheet1.Cells(n, 1)
                     If value1 = value2 Then
                      wbsb1.Range("o" & i).Value = "Found"
                     End If
                 Next
            Next
            
            For Each worksheet2 In wb2.Worksheets
                NumberOfValues3 = worksheet2.Range("A1").End(xlDown).Row
                 For o = 1 To NumberOfValues3
                  value3 = worksheet2.Cells(o, 1)
                     If value1 = value3 Then
                      wbsb1.Range("o" & i).Value = "Found"
                     End If
                 Next
            Next
        

Next
Application.Calculation = xlCalculationAutomatic
 Application.ScreenUpdating = True
 wb1.Close
  wb2.Close
    newExcel.Quit
    Set newExcel = Nothing
End Sub

从你的答案中可以看到一个三重嵌套的For循环，没有退出条件，这就是为什么在更大的数据集上运行它要花很长时间的原因。
您是在每张纸上查找该值的第一次出现，还是在每张纸上查找所有值？
看一下下面的代码，看看是否可以让它为你所需要的工作。我还没有完成第二个嵌套的For循环。

For Each worksheet1 In wb1.Worksheets
    NumberOfValues2 = worksheet1.Range("A1").End(xlDown).Row
                
    On Error Resume Next

    'Look for value1 in Range C:C in worksheet1
    value2 = worksheet1.Range("C1:C" & NumberOfValues2).Find(value1)
    If Err.Number <> 91 Then 'If the value was found
        wbsb1.Range("O" & i).Value = "Found"
    End If

    On Error GoTo 0

    'If the value was not found, move on to the next worksheet

Next

'Add the Code for your wb2.Worksheets loop