Hi,
Firstly, I think you should clean up your code (a bit)
Secondly, if you just want to stop if the amplutude is too high you can use a threshold detector (already existing in LabVIEW) and a case structure.
Lastly, you have a problem with your stop condition (in the acquisition loop) and you do not handle errors while looping this may be a problem...
Hope this helps.