Help needed determining available cash...

I've just been appointed as the treasurer (not the bookkeeper) for a church. The main issue I'm having is that most of the revenue the church receives is earmarked for budgeted expenses i.e. money coming in and sitting in a bank account is dedicated to a building project or perhaps to a missionary or to help a food bank.
My question is, how would I be able to determine what money is available and not earmarked? Perhaps there is a better way of setting up the accounts in Sage 50 so that any income with offsetting expense accounts won't show in any revenue reports?