diff --git a/AlgebraicDataflowArchitectureModel/src/application/editor/stages/ControlFlowDelegationCellEditor.java b/AlgebraicDataflowArchitectureModel/src/application/editor/stages/ControlFlowDelegationCellEditor.java
index dcd8786..eff02d8 100644
--- a/AlgebraicDataflowArchitectureModel/src/application/editor/stages/ControlFlowDelegationCellEditor.java
+++ b/AlgebraicDataflowArchitectureModel/src/application/editor/stages/ControlFlowDelegationCellEditor.java
@@ -16,6 +16,8 @@
 import application.editor.FlowCellEditor;
 import application.editor.Stage;
 import models.controlFlowModel.CallEdgeAttribute;
+import models.controlFlowModel.ControlFlowDelegator;
+import models.controlFlowModel.ObjectNode;
 import models.controlFlowModel.ObjectNodeAttribute;
 import models.dataFlowModel.PushPullValue;
 
@@ -58,6 +60,7 @@
 		if( editingCell != null) stopEditing(true);
 		
 		System.out.println("state:" + curState.name());
+		ControlFlowDelegationStage curStage = (ControlFlowDelegationStage)stage;
 		
 		switch(curState) {
 			case SELECTING_AN_EDGE:
@@ -84,17 +87,28 @@
 
 			case SHOWING_DELEGATABLE_NODES:
 				if( graphComponent.getGraph().getModel().isVertex(cellObj) ) {
+					mxCell dstCell = null;
+					if(cellObj instanceof mxCell) dstCell = (mxCell)cellObj;
+					else throw new ClassCastException();
+
 					// invocating delegation method
-					if(!(cellObj instanceof mxCell)) throw new ClassCastException();
+					CallEdgeAttribute callEdgeAttr = (CallEdgeAttribute)graphComponent.getGraph().getModel().getValue(targetEdgeCell);	
+					if(callEdgeAttr == null) return;
 					
-					((ControlFlowDelegationStage)stage)
-						.showDelegatedGraph(graphComponent.getGraph(), targetEdgeCell, (mxCell)cellObj);
+					ObjectNode dstObjNode = ((ObjectNodeAttribute)dstCell.getValue()).getObjectNode();
+					if(dstObjNode == null) throw new ClassCastException();
+					
+					if(!curStage.isExecutableDelegation(callEdgeAttr, dstObjNode)){
+						JOptionPane.showMessageDialog(graphComponent, "It's impossible for the chose object to delegate.");
+						return;
+					}
+					curStage.showDelegatedGraph(graphComponent.getGraph(), targetEdgeCell, (mxCell)cellObj);
 
 					curState = ControlFlowDelegationStageStatus.SELECTING_AN_EDGE;
 				}
 				else {
 					System.out.println("cancel showing state.");
-					((ControlFlowDelegationStage)stage).	resetAllStyleOfCells();
+					curStage.resetAllStyleOfCells();
 					curState = ControlFlowDelegationStageStatus.SELECTING_AN_EDGE;
 				}
 				break;
@@ -109,7 +123,6 @@
 
 	}
 
-	
 	/*************************************************************
 	 * [ *private ]
 	/*************************************************************
@@ -226,12 +239,6 @@
 				return;
 			}
 			
-			CallEdgeAttribute callEdgeAttr = null;
-			if(edgeCell.getValue() instanceof CallEdgeAttribute) {
-				callEdgeAttr = (CallEdgeAttribute)edgeCell.getValue();
-			}
-			else throw new ClassCastException();
-
 			if( isDuplicatedName(objName) ) {
 				JOptionPane.showMessageDialog(graphComponent, "The named object has already existed.");
 				return;