It depends what the charges are and whether the District Attorney in its discretion thinks it is an appropriate resolution. It is suggested that you retain a local criminal defense attorney to maximize your efforts to get into the program. Good luck.
ARD is a program created by statute which is administered by the District Attorney of each county. I'm uncertain from your post whether you are asking about whether a felony charge could be eligible for ARD or whether prior felony charge(s) would render a pending charge ineligible for ARD. Generally speaking ARD is only extended to people who have no prior convictions on misdemeanor or felony offenses. If your question is focused on the felony grading of a pending charge and that impact on ARD, that will be determined by the policies of your county's District Attorney. Good luck. In any event it sounds like you need to speak privately with an experienced criminal defense attorney.
You will likely not like this answer---it depends. There are times when an attorney can get an individual into ARD when they normally would not be accepted. The prior case is a huge hurdle, but may not make it impossible. Unless you have sound legal help, for all intents and purposes I view it as impossible. A good, experienced criminal defense attorney may be able to overcome this.
This is not intended as individual legal advice and there is no attorney client relationship established by this answer. It is advisable that you seek individualized legal assistance. This is not a substitute for hiring an attorney.
I assume you have been arrested for a DUI in Lancaster County. The answers is it depends. There are a number of factors the DA will consider before recommending an individual for ARD placement if there is a significant (felony) prior record. They are too numerous to list in this response. I offer free consultations. If you would like to discuss this please call for an appointment.