The Forms dataobject does not really fit your need in this case. This will show the number of lines for text or the number of rows for a Selection. The selection method will not give the correct results if a range is copied or cut and then another range is selected.

Function getClipboard()
'Add Reference:   'Reference: Microsoft Forms xx Object
    Dim MyData As DataObject
     
    On Error Resume Next
    Set MyData = New DataObject
    MyData.GetFromClipboard
    getClipboard = MyData.GetText
End Function

Sub Test_getClipboard()
  Dim s As String, lineCount As Long
  
  If Application.CutCopyMode = xlCopy Or Application.CutCopyMode = xlCut Then
    MsgBox "Row Count: " & Selection.Rows.Count
    Exit Sub
  End If
  
  s = getClipboard
  lineCount = UBound(Split(s, vbCrLf)) + 1
  MsgBox s, vbInformation, "Line Count: " & lineCount
End Sub