Dim nF, FS
nF = 86: FS = 60
ReDim X(nF), Y(nF), DelX(nF), DelY(nF), VXP(nF), VYP(nF), VX(nF), VY(nF), V(nF)

'Read in the X and Y data
DatDir$ = "D:\Kin\ABC\MyPgms\"
Open DatDir$ & "JHKick2SX1.txt" For Input As #1
   For n = 1 To nF
      Input #1, nHold, X(n)
   Next n
Close
Open DatDir$ & "JHKick2SY1.txt" For Input As #1
   For n = 1 To nF
      Input #1, nHold, Y(n)
   Next n
Close

'Compute DelX and DelY
For n = 2 To nF
   DelX(n) = (X(n) - X(n - 1))
   DelY(n) = (Y(n) - Y(n - 1))
Next n

'Compute VXP, VYP (the velocity values between frame numbers)
For n = 2 To nF
   VXP(n) = DelX(n) * FS
   VYP(n) = DelY(n) * FS
Next n

'Comput VX and VY (the velocity values at whole frame numbers)
For n = 2 To nF - 1
   VX(n) = (VXP(n) + VXP(n + 1)) * 0.5
   VY(n) = (VYP(n) + VYP(n + 1)) * 0.5
Next n

'Compute Velocity magnitude
For n = 2 To nF
   V(n) = Sqr(VX(n) ^ 2 + VY(n) ^ 2)
Next n

'Switch from exponential format to 4 decimal places
For n = 2 To nF - 1
   Vhold = CLng(V(n) * 10000)
   V(n) = Vhold / 10000
Next n

'Display the data
For n = 1 To nF
    VList$ = VList$ & Str(V(n)) & vbCrLf
Next n
TextBox1.Text = VList$
TextBox1.SetFocus

'Save the Velocity data to disk
Open DatDir$ & "JHKickToeV.txt" For Output As #1
   For n = 1 To nF
      Print #1, V(n)
   Next n
Close