Dim xlApp   As Object
Dim xlBook  As Object
Dim xlSheet As Object

Dim FileName   As String
Dim myFileName As String
Dim myShape    As Object

FileName = Environ("USERPROFILE") & "\デスクトップ\sample.xls"

Set xlApp   = CreateObject("Excel.Application")
Set xlBook  = xlApp.Workbooks.Add
Set xlSheet = xlBook.WorkSheets(1)

With xlSheet

    .Range("A18:D18").MergeCells = True       'セルを結合
    .Range("A18").HorizontalAlignment = -4108 '横位置を中央揃えに
    .Range("A18").Font.Size = 48              'フォントの大きさを変更

End With

'保存
xlBook.Saveas (FileName)

xlBook.Close

xlApp.Application.Quit

Set xlSheet = Nothing
Set xlBook = Nothing
Set xlApp = Nothing