modifier box api

This is what I want, a field that I and my players can enter a positive, or negative number and have it apply to the next roll that person makes. thanks

This already exists. You can put ?{name of query here|default value here} in any Ability or Macro. When you run the Ability or Macro it will prompt you for a value. Additionally, if you put an Ability or Macro in the chat window you can add a modifier at the end. The modifier will be placed at the very end of the macro. Example: Macro Name: #Test Macro Body: /roll 1d20+13 Chat window input: #Test +5 Chat window output: /roll 1d20+13 +5 - Gauss