Drag the CRM Validator
from the Portal Connector
widget list into the body of your form and click on the edit
button to display the properties prompt.
settings of the widget includes a FetchXML
text area for you to define a fetch that the widget will use to determine if a form submission is valid or not, based on the returned number of records.
dropdown list allows you to select a comparative operator (=, >, <=, etc.) to use against your fetch.
The Aggregate Value
numeric textfield allows you to specify a whole, positive number for the widget to compare with its results.
Please note that it is very important to ensure that the fields that you wish to validate have an alias set so that you may compare the field data to any existing records.