Monthly recurring billing based on fixed hours and how to use process configurator for this purpose

Summary:

We use rate-based billing method, and as of now the revenue and invoicing is based on the hours & expenditure type the employee is entering in OTL * the bill rate based on project role defined at contract bill plan level.

Now the requirement from business is that they want to have fixed amount to be billed monthly for few employees based on the project. How to use process configurator to create event automatically every month in this case?

For eg for certain projects they want fixed amount to be billed based on hours. Let's say for Project A they want fixed 148 hours to be billed irrespective of number of days they have entered in OTL or any leave taken.