Labview will do this very nicely. Although you could do this with a global variable they take up more memory so try this method.
step 1. open front panel of the VI that you want to copntrol. Step 2. go to the icon in the upper right hand corner and right click on the icon and select show connector Step 3. click on empty space on icon or if there is no space (right click on that connector and select add terminal) then click on the control that you want to control. Step 4 save VI and close Step 5 in main VI if VI you just modified shows up white right click on it and select relink to sub VI. Step 6 right click on the output of sub VI and select create contol and this will put it on the front panel and will allow you to control your sub vi. from there the possibilities are endless. Also if you are new to labview there is a good book that I would suggest it is called Labview for everyone by Jeffrey travis.
