Manual lock / Unlock table using Peoplecode

Our business requires Peoplesoft AR to accept transactions round the clock from multiple locations. However, we need to schedule a batch job to run nightly and during the time my custom process is running I am fetching the value of the 'NEXT' Group ID, incrementing it by the number of transactions my batch job is loading and update the last used ID. Since this is a multi step process and I donot want any onlie transaction interrupting my counter and inserts / updates, is there a way for me to use peoplecode in my app engine program and place a