Hello lyzhab,
I have some clarifying questions to ask so that I can help you moving forward:
Were you trying to use the same channel in your two original analog output tasks, or were you using different channels? Using the same channell will always give you the error that you saw.
I believe I have assembled some resources that will help you moving forward:
Simultaneous Analog Output Tasks on the Same Device
http://digital.ni.com/public.nsf/allkb/2C45C3DC484FF730862570E7007CCBD4
Since your device is an X Series device, you should be able to perform simultaneous Analog Output tasks. The next resource is a community example that shows how to implement multiple channel Analog Output simultaneously.
Multiple Channel Analog Output with Dynamically Updated Waveform Attributes
https://decibel.ni.com/content/docs/DOC-10821
This next resource includes example code that details how to control an event structure by clicking on different tabs; please let me know if this is what you were referring to or not.
Tab Control with While Loop and Event Structure Example
https://decibel.ni.com/content/docs/DOC-3522
Good luck!
Gabby
National Instruments Applications Engineer