InfoPath Dev

I am using the validation of "Cannot be blank" and nothing else in all my fields. So when the user submits the form without completing the mandatory fields an error message pops up which says " InfoPath cannot submit the form because it contains validation errors.... "
How can we change this long error message with a smaller one.

Thank you!

You need to do it using code behind the submit button.  Below is what I did in jscript.  Changing it to C+ should be easy. 

function CTRL21_7::OnClick(eventObj)
{
    var error_message = ""
  try
  { 
   
   XDocument.Submit();
  }
   
  catch (ex)
  {
   error_message = ex.message
   
   if ( ex.message.indexOf("does not contain any new data") > 0 )
    {
    XDocument.UI.Alert("Record not updated. No data has been changed.");
    }
   else
   if ( ex.message.indexOf("validation errors") > 0 )
    {
    XDocument.UI.Alert("Record not updated. There are validation errors. Errors are marked with either a red asterisk (required fields) or a red, dashed border (invalid values.");
    }
   else
   if ( ex.message.indexOf("permission denied") > 0 )
    {
    XDocument.UI.Alert("Record not updated. You do not have permission to add, delete, or update records.");
    } 
   else
   if (ex.message != "")
    {
    bracket = ex.message.indexOf("[")
    other_error = "Notify system administrator of critical error. " + ex.message.substr(bracket,500)
    XDocument.UI.Alert (other_error);
    }
   else
   if (ex.message == "")
    {
    XDocument.UI.Alert ("Draft saved successfully")
    }
  }
}

If you're not into coding, you can add conditional formatting to disable the submit button if required fields are blank, thus forcing the users to continue filling out the form.