The program then clears the control and draws axes and tick marks.

Next the program creates an MS Script control and sets its language to VB Script. It then creates a function TheFunction that takes a parameter X and returns the result given by the user-entered expression.

The program then loops over the desired X values, using the Script control's Eval method to evaluate TheFunction for the new value of X, and graphing the result.

' Graph the equation entered by the user.
Private Sub cmdGraph_Click()
Dim xmin As Single
Dim xmax As Single
Dim Dx As Single
Dim ymin As Single
Dim ymax As Single
Dim x As Single
Dim y1 As Single
Dim y2 As Single
Dim i As Integer
Dim script_control As MSScriptControl.ScriptControl

    On Error GoTo EvaluateError

    ' Get the bounds.
    xmin = CSng(txtXmin.Text)
    xmax = CSng(txtXmax.Text)
    Dx = CSng(txtDx.Text)
    ymin = CSng(txtYmin.Text)
    ymax = CSng(txtYmax.Text)

    ' Scale to fit the bounds.
    picGraph.Scale (xmin, ymax)-(xmax, ymin)

    ' Draw the graph's background.
    picGraph.Cls
    picGraph.Line (xmin, 0)-(xmax, 0), vbBlue
    picGraph.Line (0, ymin)-(0, ymax), vbBlue
    For i = 0 To xmin Step -1
        picGraph.Line (i, -0.25)-Step(0, 0.5), vbRed
    Next i
    For i = 0 To xmax
        picGraph.Line (i, -0.25)-Step(0, 0.5), vbRed
    Next i
    For i = 0 To ymin Step -1
        picGraph.Line (-0.25, i)-Step(0.5, 0), vbRed
    Next i
    For i = 0 To ymax
        picGraph.Line (-0.25, i)-Step(0.5, 0), vbRed
    Next i

    ' Make a script control.
    Set script_control = New MSScriptControl.ScriptControl
    script_control.Language = "VBScript"

    ' Define the function.
    script_control.AddCode _
        "Function TheFunction(X)" & vbCrLf & _
        "    TheFunction = " & txtExpression.Text & vbCrLf _
            & _
        "End Function"

    ' Graph the equation.
    y1 = script_control.Eval("TheFunction(" & xmin & ")")
    For x = xmin + Dx To xmax Step Dx
        ' Evaluate the next value.
        y2 = script_control.Eval("TheFunction(" & x & ")")

        ' Draw the next line.
        picGraph.Line (x - Dx, y1)-(x, y2)

        ' Save the current Y value.
        y1 = y2
    Next x
    Exit Sub

EvaluateError:
    Beep
    MsgBox Err.Description
End Sub