The zoom control is not available for the selected camera
This VB example uses the minimum and maximum zoom values to initialize the slider control:
Private SubForm_Load() Slider1.Min = ActiveDcam1.GetZoomMin
Slider1.Max = ActiveDcam1.GetZoomMax
Slider1.Value = ActiveDcam1.Zoom
If the currently selected camera doesn't support software zoom control, the method will generate an error.