Sub ex1()
Dim s As String, s1 As String
Dim i As Integer, j As Integer
s = InputBox("Введите слово")
i = InStr(s, "а")
If i > 0 Then
s1 = Left(s, i)
For j = i + 2 To Len(s) Step 2
s1 = s1 + Mid(s, j, 1)
Next j
Else
s1 = s
End If
MsgBox "Результат: " + s1
End Sub