You can make it mandatory for users in your lab to select a funding/grant code when creating a booking. To do this you will need to use the Projects feature, which is available on the Premium and Enterprise Clustermarket subscriptions.
Firstly, please ensure that Projects is turned ON in your lab's settings. Then, you will need to create the Project with a Funding/Grant code and assign it to your users. Please see the Projects help guide if you require assistance with creating a project.
In your user's settings, or in access group settings, you can then turn on the rule 'Are funding codes mandatory when creating a booking?'. This will mean that a user must
select a project to associate their booking to before they can proceed with the booking.