You can edit a function by changing its parameter values. For example, you can specify that a function include or exclude a specified member, or you can change the hierarchy value of a function.
To edit a function:
Open a report and select the data row or column or a data row or column heading cell in which you want to edit a function.
In the Selected area of the Select Members dialog box, double-click the function to edit.
Double-click the Value column inside row 1, then edit its value by clicking the Lookup button.