The Conditional Validation for Elementor Pro Form will allow you to validate a form with the same expressions used with Conditionals Fields.
Conditional Validation helps you validate your form fields before submission.
By default, the validation is disabled. For the form to be valid, all conditions must be true.
For example, if I use the condition
name == 'Joe' then for the name field, the only valid value is 'Joe', and for any other value, the form will display an error.
You can set the field id of the field where the message will display, for generic validation issues, the message will be displayed at the bottom.
There are three major options in conditional validation:
Error Message: Here you need to simply place the error message to display when the validation returns to false.
Field ID (optional): It is optional to use the Field ID to attach the error to a specific field.
There is an option to hide the Submit button: if switched on, the Submit Button will not appear at all until the condition in question is satisfied.
In Case of Performance Issue
If there are performance issues and the form contains one or more Amount fields, the "Update On" option of these should be set to "Change" and not "Input"