Excel 2007 : Sudden "freeze" while executing vba-loop

Solve: Adding in DoEvents in the code removed the random halts.

I have been exploring the more entertaining sides of excel recently, mostly by various animations performed through vb-algorithms. By manipulating the fill-color in cells, I have been able to replicate a simple snake-game, fireworks-animations and now a simple wave-simulation.

However, upon execution of any of these little programs, it seems as though the code stops executing after about 5-10 seconds or so.
Task manager says excel is using ~100% cpu for the entire execution of the program. After the program is seemingly halted, the cpu usage is still 100%, and the worksheet is "locked" as though a program was running some code on it. I need to press CTRL+break to stop the code properly, after which I can restart the code without any problems for the next 5-10 seconds.

Surely I must be missing something.

Here is the code for the wave-simulator (with no real delay, thus making the animation way too fast on any new computers):

'Some ugly coding, I know..
Dim y(300) As Double
Dim ys As Double
Dim yd As Integer
Dim temp5 As Long

Sub wave()

    init
    
    While Cells(1, 1) = "False"
    
    For temp = 300 To 1 Step -1
        Cells(CInt(y(temp)), temp).Interior.ColorIndex = Null
        y(temp) = y(temp - 1)
        Cells(CInt(y(temp)), temp).Interior.ColorIndex = 1
    Next temp
    
    If yd = 1 Then
        If ys > 1 Then
            yd = -1
            ys = -0.1
        End If
    ElseIf yd = -1 Then
        If ys < -1 Then
            yd = 1
            ys = 0.1
        End If
    End If
    ys = ys / 0.9
    
    Cells(CInt(y(0)), 1).Interior.ColorIndex = Null
    y(0) = y(0) + ys
    Cells(CInt(y(0)), 1).Interior.ColorIndex = 1
    
    Wend

End Sub

Sub init()

Cells(1, 1) = "False"
For temp = 0 To 300
    Cells(20, temp + 1).Interior.ColorIndex = 1
    y(temp) = 20
Next temp
ys = 1#
yd = 1
End Sub

try adding a DoEvents inside the While/Wend loop.

    Cells(CInt(y(0)), 1).Interior.ColorIndex = Null
    y(0) = y(0) + ys
    Cells(CInt(y(0)), 1).Interior.ColorIndex = 1
    DoEvents
    Wend

End Sub