请教各位大佬，求到补码后如何符号位取反变成移码？

求补码的代码如下：
Dim a(16) As Integer, x As Integer
x = CInt(Text1.Text)
If x >= 0 Then a(16) = 0 Else a(16) = 1
x = Abs(x)
For i = 1 To 15
a(i) = x Mod 2
x = x \ 2
Text2.Text = ""
Next i
For i = 16 To 1 Step -1
Next i
For i = 1 To 15
a(i) = 1 - a(i)
Next i
Text2.Text = a(16)
For i = 15 To 1 Step -1
Next i
Text2.Text = a(16)
a(1) = a(1) + 1
i = 1
While a(i) = 2 And i < 15
a(i) = 0
a(i + 1) = a(i + 1) + 1
i = i + 1
Wend
For i = 15 To 1 Step -1
Text2.Text = Text2.Text & a(i)
Next i

但是VB好像没有符号位取反的运算符，想问大佬们如何解决