Public Function ValidateDCR_RoutingNum(ByVal RoutingNum As String, ByVal AccountNum As String) As String
        '<Steven Potter> 01/07/2010
        'Validate Account Information 
        Dim Msg As String = Nothing
        Dim ilValid As Boolean = False
        ilValid = oRoutingValidation.validateinfo(RoutingNum, AccountNum)
        If ilValid = False Then
            Msg = "Invalid Routing Number Entered"
            AddErrorProviderBrokenRule("DCR_RoutingNum", Msg)
        End If
        Return Msg
        '<Steven Potter>
    End Function

But I think your missing the point here. At the end of CHeckRulesHook its returning a boolean value

return Me.ErrorProviderBrokenRuleCount = 0

this was code added by the BO generator.
mmBusiness Object is storeing that value to

mmSaveDataResult Result = mmSaveDataResult.RulesPassed;

Heres the full code

/// <summary>
		/// Checks the business object's rules
		/// </summary>
		/// <param name="businessObject">Business object</param>
		/// <param name="ds">DataSet</param>
		/// <param name="tableName">DataTable name</param>
		/// <returns>mmSaveDataResult enumerated value</returns>
		protected virtual mmSaveDataResult CheckRules(mmBusinessObject businessObject, DataSet ds, string tableName)
		{
			mmSaveDataResult Result = mmSaveDataResult.RulesPassed;

			if (businessObject.AutoCheckRules)
			{
				if (businessObject.BusinessRuleObj != null)
				{
					// Store the current row number and row on the business rule object
					businessObject.BusinessRuleObj.CurrentRow = businessObject.RowNum;
					businessObject.BusinessRuleObj.DataRow = businessObject.DataRow;

					// Check the business rules
					Result = businessObject.BusinessRuleObj.CheckRules(ds, tableName, 
						businessObject.UseErrorProvider);
				}

				// Check any child object business rules
				mmSaveDataResult ChildResult;

				foreach (mmBusinessObject ChildBizObj in businessObject.RefBizObj)
				{
					if (ChildBizObj.AutoSaveOnParentSaved && ChildBizObj.GetCurrentDataSet() != null)
					{
						// Call Save PreProcess method on the child object. This ensures any
						// EndEdit or setting of parent foreign keys is done before checking rules
						if (ChildBizObj.PreSaveProcessing(ChildBizObj.GetCurrentDataSet(), ChildBizObj.TableName))
						{
							// Make a recursive call to check the child object's business rules
							ChildResult = this.CheckRules(ChildBizObj, ChildBizObj.GetCurrentDataSet(),
								ChildBizObj.TableName);

							// Set RulesChecked flag
							ChildBizObj.RulesCheckedByParent = true;

							// Store the ChildResult in the overall Result variable if the severity is
							// greater than the current setting
							if (ChildResult == mmSaveDataResult.RulesBroken)
							{
								// Clear the RulesChecked flag since the rules failed
								ChildBizObj.RulesCheckedByParent = false;
								Result = ChildResult;
							}
							else if (ChildResult == mmSaveDataResult.RuleWarnings && Result == mmSaveDataResult.RulesPassed)
							{
								Result = ChildResult;
							}
						}
						else
						{
							Result = mmSaveDataResult.SaveCanceled;
							break; // Bail out if the child object's PreSaveProcessing returns false
						}
					}
				}
			}
			return Result;
		}