アルファベットをカナに変換

事前設定：Microsoft Scripting Runtimeへの参照設定

Function ConvertAlphabetToKatakana(str As String) As String
    Dim alphaToKana As Dictionary
    Set alphaToKana = New Dictionary
    
    ' アルファベットとカタカナの対応表
    alphaToKana.CompareMode = vbTextCompare ' 大文字小文字を区別しない
    alphaToKana.Add "A", "エー"
    alphaToKana.Add "B", "ビー"
    alphaToKana.Add "C", "シー"
    alphaToKana.Add "D", "ディー"
    alphaToKana.Add "E", "イー"
    alphaToKana.Add "F", "エフ"
    alphaToKana.Add "G", "ジー"
    alphaToKana.Add "H", "エイチ"
    alphaToKana.Add "I", "アイ"
    alphaToKana.Add "J", "ジェー"
    alphaToKana.Add "K", "ケー"
    alphaToKana.Add "L", "エル"
    alphaToKana.Add "M", "エム"
    alphaToKana.Add "N", "エヌ"
    alphaToKana.Add "O", "オー"
    alphaToKana.Add "P", "ピー"
    alphaToKana.Add "Q", "キュー"
    alphaToKana.Add "R", "アール"
    alphaToKana.Add "S", "エス"
    alphaToKana.Add "T", "ティー"
    alphaToKana.Add "U", "ユー"
    alphaToKana.Add "V", "ブイ"
    alphaToKana.Add "W", "ダブリュー"
    alphaToKana.Add "X", "エックス"
    alphaToKana.Add "Y", "ワイ"
    alphaToKana.Add "Z", "ゼット"
    
    Dim result As String
    Dim i As Integer
    For i = 1 To Len(str)
        Dim ch As String
        ch = Mid(str, i, 1)
        If alphaToKana.Exists(UCase(ch)) Then
            result = result & alphaToKana(UCase(ch))
        Else
            result = result & ch ' 対応するカタカナがない場合はそのまま追加
        End If
    Next i
    
    ConvertAlphabetToKatakana = result
End Function