I understand that you want to simulate some digital logic to check that it perfoms the function you require and to see the output.
Without knowing the complexity of your schematic, I can only suggest a simple way of generally testing some logic.
You can supply logic gates in Multisim with an 'Interactive Digital Constant' which can be controlled by a key on your keyboard so it can easily be toggled. You will then need some sort of indicator to show you the output from the logic system. A Virtual LED connected from the output of the gates to a Digital Ground would work fine.
Presumably you are aware that you must then run your simulation by pressing the <F5> key (or clicking the green play button just above your schematic).
Once the simulation is running, you can then toggle the Interactive Digital Constants with the assigned keys or by left clicking on them.
I've attached a very simple schematic to give you an idea of what I'm referring to.
Hopefully that will give you something to try. If there is anything else I can assist you with regarding this issue, please don't hesitate to post.
Oli LabVIEW Student Ambassador National Instruments UK
You should post your questions regarding Multisim in the Multisim board. While there may be some folks who frequent the LabVIEW board who use Multisim, you will get more exposure in the forum that's specifically geared towards the product you are using.