Dim As Integer n = 0, sum = 0
Dim As Single i

Do
    Input "Enter integral rainfall (99999 to quit): ", i
    If i = 99999 Then
        Exit Do
    Elseif (i < 0) Or (i <> Int(i)) Then
        Print "Must be an integer no less than 0, try again."
    Else
        n += 1
        sum += i
        Print "  The current average rainfall is"; sum/n
    End If
Loop

Sleep