Const Wi As Long = 200
Const He As Long = 200
Const MaxI As Long = 1023
Dim TLX, TLY, BRX, BRY As Double
Public Sub Init()
    Me.Range(Cells(1, 1), Cells(He, Wi)).ColumnWidth = 0.5
    Me.Range(Cells(1, 1), Cells(He, Wi)).RowHeight = 5
    TLX = -2
    TLY = 2
    BRX = 2
    BRY = -2
    Me.Range(Cells(1, 1), Cells(He, Wi)).Select
End Sub
Private Sub Mandel(ByVal Target As Range)
    Dim x1, y1, zr, zi, cr, ci As Double
    x1 = (BRX - TLX) / Wi
    y1 = (TLY - BRY) / He
    TLX = TLX + x1 * (Target.Columns(1).Column - 1)
    BRX = TLX + x1 * Target.Columns.Count
    TLY = TLY - y1 * (Target.Rows(1).Row - 1)
    BRY = TLY - y1 * Target.Rows.Count
    x1 = (BRX - TLX) / Wi
    y1 = (TLY - BRY) / He

    For y = 1 To He
        For x = 1 To Wi
            cr = TLX + x * x1
            ci = TLY - y * y1
            zr = 0
            zi = 0
            For i = 0 To MaxI
                zrs = zr * zr
                zis = zi * zi
                If zrs + zis > 4 Then Exit For
                zi = 2 * zr * zi + ci
                zr = zrs - zis + cr
            Next
            Me.Cells(y, x).Interior.Color = RGB((5 * i) Mod 256, (4 * i) Mod 256, (3 * i) Mod 256)
        Next
    Next
End Sub
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
    If (Intersect(Me.Range(Cells(1, 1), Cells(He, Wi)), Target).Rows.Count > 2) And (Intersect(Me.Range(Cells(1, 1), Cells(He, Wi)), Target).Columns.Count > 2) Then
        Call Mandel(Intersect(Me.Range(Cells(1, 1), Cells(He, Wi)), Target))
        Me.Cells(1, 1).Select
    End If
End Sub