Function ПростаяДробь(var As Double) As String
Dim ЧислоДесЗнаков As Long, strVar As String, pointPosition As Long, Delimiter As String
    
    Delimiter = Mid(FormatNumber(123.45, 2), 4, 1)
    strVar = Format(var)
    pointPosition = InStr(strVar, Delimiter)
    
    ЧислоДесЗнаков = Len(Right(strVar, Len(strVar) - pointPosition))
    ПростаяДробь = Format(var * 10 ^ ЧислоДесЗнаков, "0") & "/" & Format(10 ^ ЧислоДесЗнаков, "0")
End Function