http://www.hslda.org/laws/default.asp?State=MD
Option 2 is to:
Provide home instruction under the supervision of a church institution or school that complies with regulations.
Is it a church school? If it is, that makes things easy, since the regulations leave the choice of attendance and subjects up to the school, not the state. You're good to go as long as you can convince them to let you homeschool part-time.
If it's not a church school, things will get somewhat more complicated, but not overly much so. Your program must have "regular, thorough instruction" in certain subjects, and you have to keep a portfolio of work, but no qualifications are made as to where the instruction has to take place, and no specifics are given as to how many hours you have to put in yearly. Bottom line, you should have no problems counting school attendance as part of your homeschool program. Just to be safe though, you might want to join
Home School Legal Defense Association (HSLDA).