I am trying to use Gravity Forms to make a payment page in WordPress. The first three fields are customers name, order number and postcode and the last one is eway payment. I want to check the customer's name, order number and postcode through an Excel form before make payment. If the validation is successful, the last section will be active. Are there any add_ons or do I need to change the code? I actually have the code but I do not know where to put it. Thanks.
Gravity Forms does have a couple of hooks you can use in your theme functions file or a custom functionality plugin to perform your own validation.
The gform_field_validation filter can be used to perform custom validation of a specific field.
The gform_validation filter can be used to validate the entire form.