If a person has several weeks/hours of vacation can they apply for VTO to avoid using their accrued vacation?

An employee can apply for VTO for any reason.  Deciding whether to grant VTO is discretionary, but you should have a good business reason when you deny a VTO request. An example of a good business reason for denying VTO might be that the unit staffing is planned with everyone working full-time so there is not staffing available to backfill if one employee takes extra time off on top of the allotted vacation time.