Use a PictureBox's ScaleLeft, ScaleWidth, ScaleTop, and ScaleHeight properties to set its scale factors so it shows only the part of the graph that should be visible. Then draw only the area that should be visible at any given time.
With this method, you can make an "infinitely" wide graph without creating a huge PictureBox holding the entire graph.

' Draw the piece of the graph that should be visible now.
Private Sub DrawGraph()
Dim wid As Single
Dim hgt As Single
Dim xmin As Single
Dim xmax As Single
Dim X As Single
Dim Y As Single
' Clear.
picGraph.Line (picGraph.ScaleLeft, _
picGraph.ScaleTop)Step(picGraph.ScaleWidth, _
picGraph.ScaleHeight), picGraph.BackColor, BF
' Give the PictureBox a scale
' so we can draw in real coordinates.
picGraph.ScaleMode = vbPixels
wid = picGraph.ScaleWidth
hgt = picGraph.ScaleHeight
picGraph.ScaleTop = hgt / 2
picGraph.ScaleHeight = hgt
xmin = scrGraph.Value
xmax = xmin + wid
picGraph.ScaleLeft = xmin
picGraph.ScaleWidth = wid
' Draw the axis.
picGraph.Line (xmin, 0)(xmax, 0), vbBlack
X = 25 * (xmin \ 25)
Do While X < xmax
X = X + 25
If X Mod 100 = 0 Then
picGraph.Line (X, 7)Step(0, 14), vbBlack
picGraph.CurrentX = X  picGraph.TextWidth(X) / _
2
picGraph.CurrentY = 10
picGraph.Print X
Else
picGraph.Line (X, 3)Step(0, 6), vbBlack
End If
Loop
' F(X) = 40 * Sin(X / 10) + 20 * Cos(X / 7)
X = xmin
picGraph.CurrentX = X
picGraph.CurrentY = 40 * Sin(X / 10) + 20 * Cos(X / 7)
Do While X < xmax
X = X + 1
picGraph.Line (X, 40 * Sin(X / 10) + 20 * Cos(X / _
7)), vbRed
Loop
' F(X) = 20 * Sin(X / 20)
X = xmin
picGraph.CurrentX = X
picGraph.CurrentY = 20 * Sin(X / 20)
Do While X < xmax
X = X + 1
picGraph.Line (X, 20 * Sin(X / 20)), vbBlue
Loop
' F(X) = 40 * Sin(X / 11) * Cos(X / 13)
X = xmin
picGraph.CurrentX = X
picGraph.CurrentY = 40 * Sin(X / 11) * Cos(X / 13)
Do While X < xmax
X = X + 1
picGraph.Line (X, 40 * Sin(X / 11) * Cos(X / 13)), _
vbWhite
Loop
picGraph.Picture = picGraph.Image
End Sub
