Sub LoadData()
    Dim aRange As Range
    Dim aIndex As Integer
    Dim aOpened As Boolean
    Dim aFilename As String
    Dim aWorkbook As Workbook
    
    Set aRange = Range("C3:E5")
    For aIndex = 1 To aRange.Rows.Count
        aFilename = "Vzorek " & aIndex & ".xlsx"
        On Error Resume Next
        Set aWorkbook = Workbooks(aFilename)
        On Error GoTo 0
        If aWorkbook Is Nothing Then
            Set aWorkbook = Workbooks.Open(ThisWorkbook.Path & "\" & aFilename)
            aOpened = True
        End If
        aRange.Cells(aIndex, 1).Value = aWorkbook.Worksheets("Povrch").Range("B5")
        aRange.Cells(aIndex, 2).Value = aWorkbook.Worksheets("Objem").Range("C5")
        aRange.Cells(aIndex, 3).Value = aWorkbook.Worksheets("Poloměr").Range("D5")
        If aOpened Then
            aWorkbook.Close False
            aOpened = False
        End If
        Set aWorkbook = Nothing
    Next aIndex
End Sub