run time error 6

morning everyone hoping you could help out. below is code for extracting the x and y parameters for a spline function. i am getting a run time error 6 at the bold line, when j=7, step=32767, nstep=630.

tips/suggestions would be incredible. please and thanks

Sub plotter()
'Data sizing
Dim x(126) As Double, y(126) As Double, norder As Integer, nstep As Integer
Dim h(126) As Double
Dim i As Integer, j As Integer, step As Integer
Dim B(126) As Double, D(126) As Double, A(126) As Double, C(126) As Double
Dim xs As Double, ys As Double

'Read in data-point order
norder = ActiveSheet.Cells(3, 3)

'Read in Cubic properties
For i = 1 To norder
    x(i) = ActiveSheet.Cells(4 + i, 3)
    h(i) = ActiveSheet.Cells(4 + i, 5)
    A(i) = ActiveSheet.Cells(4 + i, 8)
    B(i) = ActiveSheet.Cells(4 + i, 9)
    C(i) = ActiveSheet.Cells(4 + i, 10)
    D(i) = ActiveSheet.Cells(4 + i, 11)
Next i

'Read in steps
nstep = ActiveSheet.Cells(3, 1)

'Determine and write out x,Y
step = 1
For i = 1 To (norder - 1) 'Discrete function step
    For j = 1 To nstep
        step = step + 1
        xs = x(i) + (h(i) / nstep) * (j - 1)
        ys = A(i) * (xs - x(i)) ^ 3 + B(i) * (xs - x(i)) ^ 2 + C(i) * (xs - x(i)) + D(i)
        ActiveSheet.Cells(step, 15) = xs
        ActiveSheet.Cells(step, 16) = ys
    Next j
Next i

End Sub

i changed the dimensions from integer to long. will give that a shot

declare step as Long
right now you have it as integer so you can only index up to 32,767

Best Regards