Greetings!
1) You could change the simulation stop time in
simulink. The process to do that is explained in p-10 of the following
link -
http://www.ni.com/pdf/manuals/370420b.pdf
2) In LabVIEW you have simulation time vi, this returns
the current simulation time. This value is useful if you terminate the
simulation before the final time and you need to know the time at which
the simulation terminated. This value is also useful if you want to
generate a signal based upon the simulation time without using the
Signal Generation functions.
There is no direct method to vary the simulation stop time in simulink from LabVIEW
Hope this helps. Good luck
Best regards
Avi Harjani