Dat zijn nog eens queries:

SELECT	tblWorkFlowEntry.wfe_ID AS task_ID,
	tblNodes.node_modified AS date,
	'WFE' AS task_type,
	tblWorkFlowEntry.wfe_description AS task_description,
	tblWorkFlow.ws_user_ID AS task_from_user_ID,
	tblNodes.node_ID AS task_node_ID,
	'' AS task_data

FROM	tblNodes
	LEFT JOIN tblWorkFlowEntry
	  ON tblWorkFlowEntry.wfe_ID = tblNodes.node_wfe_ID
	LEFT JOIN tblWorkFlow
	  ON tblWorkFlow.workflow_ID = tblWorkFlowEntry.wfe_workflow_ID
	
WHERE	tblWorkFlowEntry.wfe_userGroup_ID IN (#groups#)
  AND	tblNodes.node_wfe_complete=FALSE

UNION

SELECT	tblWorkFlowValidation.wfv_ID AS task_ID,
	tblNodes.node_modified AS date,
	'WFV' AS task_type,
	tblWorkFlowValidation.wfv_description AS task_description,
	tblWorkFlow.ws_user_ID AS task_from_user_ID,
	tblNodes.node_ID AS task_node_ID,
	'' AS task_data

FROM	tblNodes
	LEFT JOIN tblWorkFlowEntry
	  ON tblWorkFlowEntry.wfe_ID = tblNodes.node_wfe_ID
	LEFT JOIN tblWorkFlow
	  ON tblWorkFlow.workflow_ID = tblWorkFlowEntry.wfe_workflow_ID
	INNER JOIN tblWorkFlowValidation
	  ON tblWorkFlowValidation.wfv_wfe_ID = tblWorkFlowEntry.wfe_ID
	LEFT JOIN tblUserGroup_WorkFlowValidation
	  ON tblUserGroup_WorkFlowValidation.uwfv_wfv_ID = 
                     tblWorkFlowValidation.wfv_ID

WHERE	tblUserGroup_WorkFlowValidation.uwfv_userGroup_ID IN (#groups#)
  AND	tblNodes.node_wfe_complete=TRUE
  AND	NOT EXISTS (
		SELECT	*
		FROM	tblNodes_WorkFlowValidation
		WHERE	nwfv_node_ID=tblNodes.node_ID
		  AND	nwfv_wfv_ID=tblWorkFlowValidation.wfv_ID
	)

UNION

SELECT	task_ID,
	task_type,
	task_date AS date,
	task_description,
	task_from_user_ID,
	task_node_ID,
	task_data
FROM tblTasks
WHERE task_userGroup_ID IN (#groups#)

ORDER BY date

Go Stijn!