A system for dynamically integrating changes in rules governing business operations into a rule-implementing application program includes a dynamic business logic rule integrator ("DBLRI") that provides rules to the application software as executable routines. The DBLRI presents to a user one or more GUIs through which the user writes functional-language expressions for the rules. The GUIs provide menus of associated functions, operators and parameters that are available for use. The set of parameters associated with a given GUI is dynamically updated, to correspond to changes in the underlying business logic rules. The user writes and/or edits the expressions by selectively combining the available functions, operators and parameters. The DBLRI evaluates the functional expressions and produces associated executable parse trees or DLLs, which the application software then calls at appropriate times. The DBLRI operates also with a dynamically configurable database that provides parameters required for the rules as the rules are updated, added and/or revised.