1. An availability control feature in a financial management system, comprising: a budget data structure having budget nodes, the budget nodes storing data representing available budget and expenditure items admitted to the financial management system, a rule array consisting of one or more than one independent rule sets, each rule set having a plurality of control objects that include an address field pointing to one or more nodes of the budget data structure, a test field defining a relationship that is to be maintained between budget items and expenditure items and a response field, and an AVC manager, responsive to a new transaction that proposes to add a new expenditure value to at least one budget node, to execute all rules of the rule array that are related to the budget nodes of the new transaction and to block the transaction if at least one rule generates an error.