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# OnBeforeChange Event

Occurs after changes to a form's underlying XML document have been made but before the changes are accepted.

Function node::OnBeforeChange(ByRef pDataDOMEvent As DataDOMEvent)

pDataDOMEvent Required DataDOMEvent. A reference to the DataDOMEvent object.

## Remarks

This event handler allows users to cancel an operation.

During the OnBeforeChange event, the form's underlying XML document is placed in read-only mode. If the ReturnStatus property of the DataDOMEvent object is set to False, Microsoft Office InfoPath 2003 rejects the changes that were made and a message box is displayed to the user. If an error occurs in the scripting code for the OnBeforeChange event handler, InfoPath rejects the changes and restores the data to its previous state.

Notes

- It is best to avoid switching views during the OnBeforeChange event; changes have not yet been accepted, and switching to another view may result in an error.
- In some cases, events related to changes in a form's underlying XML document may occur more than once. For example, when existing data is changed, an insert and delete operation occurs.
- If a validation error is encountered in any OnBeforeChange event handler, the document fails to load. A `try-catch` block in the OnLoad event can be used to catch this validation failure and to load the document despite the error.

## Example

In the following example from the Events developer sample form, the OnBeforeChange event handler is used to validate the data in a field. If the data is not valid, the ReturnStatus property of the DataDOMEvent object is used to reject the changes.

    function msoxd__RepVisitDt::OnBeforeChange(eventObj)
    {
       var oNode = XDocument.DOM.selectSingleNode
          ("/Customers/CustomerInfo/ContactDates/PhoneContactDt");

       if (!oNode.text)
       {
          eventObj.ReturnMessage = "The Phone Contact Start date must be
             set prior to the Representative Visit date.";
          eventObj.ReturnStatus = false;
          return;
       }

       // If the data is valid, eventObj.ReturnStatus = true.
       eventObj.ReturnStatus = true;
       return;
    }

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