Spread is designed to keep the active viewport in sync with the active cell. If the active cell is in a frozen row or column then the active viewport should be a frozen viewport. If the active cell is in a frozen viewport and you want to set a non-frozen viewport to be active, you can move the active cell to a scrollable row and then set the active viewport to the desired scrollable viewport. Use the SetActiveCell method and then use this SetActiveViewport method.

Reference

SpreadView Class
SpreadView Members

User-Task Documentation

Customizing Viewports