If you are using two separate case structures to write to the same numeric control, you can use a local variable write (instead of a global variable, though a global write will work) to update the numeric control. In LabVIEW, a wire can only have one source, so you would not be able to wire the two outputs from the independent case structure together without some logic to determine one unique output at any given time. Using local variables in your situation will resolve your multiple source error.
Regards,
Wilbur Shen
