This gives you names and sizes for all .xls files in the directory
containing the open workbook:
Sub dir_test()
   Dim fs, f, s
   Dim filespec As String
   Dim count As Integer
   count = 1
   Set fs = CreateObject("Scripting.FileSystemObject")
   filespec = Dir(ActiveWorkbook.Path & "\*.xls")
   Do While filespec <> ""
       Set f = fs.GetFile(filespec)
       s = f.Size
       n = f.Name
       Range("A" & count) = n
       Range("B" & count) = s & " KB"
       filespec = Dir
       count = count + 1
   Loop
End Sub

For one specific file:
Sub dir_test()
   Dim fs, f
   
   Set fs = CreateObject("Scripting.FileSystemObject")
   Set f = fs.GetFile("H:\excel\Dir1.xls")

   Range("A1") = f.Name
   Range("B1") = f.Size & " KB"

End Sub