request field validation

I'm testing an API passing a string value(e.g. "ABC") to a numeric field. The input value is sent from an excel file. If I run the test, the transaction does not happen, and I get error message that says something like "ABC" is not a numeric value. My test node is using Input Mode: Form JSON, but it doesn't need to be this…

I have to validate that a field in request of a Rest API is having YYYY-MM-DDThh:mm:ss.sssZ format. Any help is most welcome. TIA