How to create a validation rule in Self Service Procurement (SSP) under Redwood UI using VBS?

Summary:

The use case is that while submitting the requisition, the requestor should see a prompt if there is specific purchasing category and a deliver to location is selected.

We have been trying to create the prompt/validation through VBS, when we are trying to see the preview the requisition gets submitted without giving any notificaiton or prompt.

Is there any other project which had a similar requirement?

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Version (include the version you are using, if applicable):

Version: 25C

Code Snippet (add any code snippets that support your topic, if applicable):