form

You should use a drop-down field for that.

var field = this.getField("myField");
field.setAction("Validate", "if(event.value != 0 && event.value != 5) {app.alert('Only 0 or 5 are allowed'); event.rc = false;}");

In this example, myField is the name of the field you want to validate. The setAction method is used to set a validation action for the field. The validation action is a JavaScript function that checks if the value entered in the field is not 0 and not 5. If the value is not valid, an alert message is displayed and the value is not accepted (event.rc = false).

You can add this code to the JavaScript section of your PDF form. You can access this section by opening the form in Adobe Acrobat, selecting Tools > Prepare Form, and then clicking on the More button and selecting JavaScript.