I am not sure how much of the program you need help with. There are several shipping examples for function generators. (open LabVIEW >> help >> find examples). These can be used to create sine waves so that you subjects can follow for breathing.
Is this want you need? There are many people on the forum that are glad to help if postings contain sufficient information to generate an answer. I did not include any code because you did not list your version of LabVIEW.
