Option Explicit

Sub CalculateAverage()
Dim total As Double
Dim count As Integer
Dim average As Double
Dim number As Double

count = 0
total = 0
Do
number = InputBox("Введите число (для выхода введите 0):")
If number <> 0 Then
total = total + number
count = count + 1
average = total / count
MsgBox "Среднее значение: " & average
End If
Loop Until number = 0

End Sub

Sub Main()
CalculateAverage
End Sub