Составить программу, в которой вставить в массив по одному элементу перед всеми отрицательными, не используя дополнительных массивов

Private Sub CommandButton1_Click()
Dim a() As Integer, n As Integer, i As Integer, k As Integer, k1 As Integer, k2 As Integer, s As Integer, z As Integer
Cells.Clear
z = 100
n = InputBox("ââåäèòå ÷èñëî ýëåìåíòîâ", , "24")
ReDim a(n) As Integer
For i = 1 To n
  a(i) = Int(Rnd * 55) - 15
  Cells(i, 1) = a(i)
Next i
For i = 1 To n
  If a(i) < 0 Then
a(i - 1) = z
  End If
Next i
For i = 1 To n
  Cells(i, 2) = a(i)
Next i
End Sub

For i = 1 To ...
If a(i) < 0 Then a(i - 1) = ...

Sub aa()
Dim a() As Integer
Cells.Clear
z = 100
n = InputBox("введите число элементов", , "24")
ReDim a(n)
Randomize
For i = 1 To n
  a(i) = Round(Rnd * 55) - 15
  Cells(i, 1) = a(i)
Next i
i = 1
Do
  If a(i) < 0 Then
    n = n + 1
    ReDim Preserve a(n)
    For j = n To i + 1 Step -1
        a(j) = a(j - 1)
    Next j
    a(i) = z
    i = i + 1
  End If
  i = i + 1
Loop Until i = n + 1
For i = 1 To n
  Cells(i, 2) = a(i)
Next i
End Sub

Sub aaa()
Dim a() As Integer, i%, n%, j%, z%
Cells.Clear
z = 100
n = InputBox("введите число элементов", , "24")
ReDim a(1 To n)
Randomize
For i = 1 To n
  a(i) = Round(Rnd * 55) - 15
Next i
[A1].Resize(n) = Application.Transpose(a)
For i = n To 1 Step -1
  If a(i) < 0 Then
    n = n + 1
    ReDim Preserve a(1 To n)
    For j = n To i + 1 Step -1
        a(j) = a(j - 1)
    Next j
    a(i) = z
  End If
Next i
[B1].Resize(UBound(a)) = Application.Transpose(a)
End Sub