'El ejemplo esta hecho para tecla TAB, pero puedes hacerlo para cualquiera

Option Explicit
Private Declare Sub Keybd_Event Lib "User32" (ByVal bVk As Byte, ByVal bScan As Byte, ByVal dwFlags As Long, ByVal dwExtraInfo As Long)
Private Const VK_TAB = &H9
Private Const KEYEVENTF_EXTENDEDKEY = &H1
Private Const KEYEVENTF_KEYUP = &H2

Public Sub SendTab()
    Keybd_Event VK_TAB, &H9, KEYEVENTF_EXTENDEDKEY Or 0, 0
    Keybd_Event VK_TAB, &H9, KEYEVENTF_EXTENDEDKEY Or KEYEVENTF_KEYUP, 0
End Sub