The tcLegendScrollBar tool is designed to show the items in the legend that don't fit in the legend rectangle, not to limit the number of characters shown in the items. Here it is an example usign it:
Private Sub Form_Load()
TChart1.Aspect.View3D = False
Dim i As Integer
For i = 0 To 10
TChart1.AddSeries scFastLine
TChart1.Series(i).FillSampleValues 10
TChart1.Series(i).Title = "this is a very very veeeeeeery long string to be shown in the legend as title for the series " + Str$(i)
Next i
TChart1.Legend.MaxNumRows = 5
TChart1.Tools.Add tcLegendScrollBar
End Sub
To limit the length of the strings in the legend you can use the OnGetLegendText event. Ie:
Private Sub TChart1_OnGetLegendText(ByVal LegendStyle As Long, ByVal ValueIndex As Long, LegendText As String)
LegendText = Left$(LegendText, 10) + "..."
End Sub