Hi Quan, you can add the expression to a text box to check the value returned, after setting the expression that retruns the value you wants you can add an action to the same text box, and check if clicking it works as you want. If it works ok, the same action OnOpen should work.
Maybe has something to do with Metric_Charge_Actual_CurrentMonth_EPSI having more than one value, in this case adding a Max() or some other funcion that returns only one value con solve this.
