VB变量当前范围内声明重复

在按钮1里面是永远不能引用到模块定义的a吗？
Private a%
Private Sub Command1_Click()
a = a + 7
Print a
Dim a%
a = a + 7
Print a
End Sub
Private Sub Command2_Click()
a = a + 7
Print a
End Sub