Is Excel VBA's Rnd() really this bad?

I need a pseudo random number generator for 2D Monte Carlo simulation that doesn't have the characteristic hyperplanes that you get with simple LCGs. I tested the random number generator Rnd() in Excel 2013 using the following code (takes about 5 secs to run):

Sub ZoomRNG()
'
Randomize
For i = 1 To 1000
    Found = False
    Do
        x = Rnd()   ' 2 random numbers between 0.0 and 1.0
        y = Rnd()
        If ((x > 0.5) And (x < 0.51)) Then
            If ((y > 0.5) And (y < 0.51)) Then
                ' Write if both x & y in a narrow range
                Cells(i, 1) = i
                Cells(i, 2) = x
                Cells(i, 3) = y
                Found = True
            End If
        End If
    Loop While (Not Found)
Next i

End Sub

Here is a simple Plot of x vs y from running the above code. Not only is it not very random-looking, it has more obvious hyperplanes than the infamous RANDU algorithm does in 2D. Basically, am I using the function incorrectly or is the Rnd() function in VBA actually not the least bit usable?

For comparison, here's what I get for the Mersenne Twister MT19937 in c++.