Hi,
I had a look at your multisim circuit. You have put a clock source there, and you are connecting a voltage inpout (LabVIEW IO) to the same point in the circuit. This is causing a clash. You should remove your clock signal from the multisim design, and give that clock signal from LabVIEW as input. From your VI, I assume that you are trying to control the amplitude of your clock signal. One way of doing that is as follows
Chinmay Anand Misra
CLD
Technical Marketing Engineer
NI IndRA