If you want to convert any number to letter then you can use this micro. Its easy to implement just you create new micro and paste this code then in any cell you can call that function.
Function ConvertToLetter(iCol As Integer) As String
' Dim iAlpha As Integer
' Dim iRemainder As Integer
' iAlpha = Int(iCol / 27)
' iRemainder = iCol - (iAlpha * 26)
' If iAlpha > 0 Then
' ConvertToLetter = Chr(iAlpha + 64)
' End If
' If iRemainder > 0 Then
' ConvertToLetter = ConvertToLetter & Chr(iRemainder + 64)
' End If
Dim columnName As String
Dim modulo As Integer
While iCol > 0
modulo = (iCol - 1) Mod 26
columnName = Chr(65 + modulo) + columnName
iCol = Int((iCol - modulo) / 26)
Wend
ConvertToLetter = columnName
End Function