Hi John,
You might take a look at an app I am developing called Software - Master (TM). It is an accounting application and handles payroll. Once the gross amount earned by an employee is calculated, the program automatically calculates federal withholding and social security.
Texas does not have a state income tax so we do need to worry about withholding from gross pay at a state level down here. The payroll app does not currently support automatic calculation of state withholding, so if Maryland has a state income tax, it would be necessary to look this up in your state withholding tables and enter it manually into the program.
All source code is provided with the purchase of the app.
The app is near completion and is very functional at this point.
To see if the app provides the info you want to make available to you management app, you could download a demo at:
https://www.smvfp.com