If you aren't already using the cypress or DIO on the driverstation, we found it was the quickest way to change Autonomous modes.
It uses the WPILib->Driverstation->CompatibilityIO->GetDigIn.vi and a Boolean array to number conversion.
To change the mode you just flip the switches to the right binary representation of the mode number on the driverstation io panel.

__________________
4 year 2011 - 2014 FRC team 308 member, Lead Programmer - C++ / LabVIEW
3 year 2011, 2013, 2014 OCCRA member, Co-Captain OCCRA team 308
- OCCRA Engineering Excellence - Waterford Kettering 2013
- Innovation in Control - 2011
- Quality award- Northville 2012
- Engineering Excellence- Howell 2014
- Innovation in Controls- Livonia 2014