Post Hubspot Form Data to an External System and Return Results

We have a client that would like to have their Hubspot Hosted Form submit the field data to their system, check to see if the entry is valid and then return a message based on whether the fields are correct or invalid.

This is new to us so we are hoping there is a developer here who can help with this.

Hi @dforsythe11 , what is the external system? Does the result of the field check need to be saved back to Hubspot?