Creating a Function Call Expression 
In the Object Manager panel, under the Detail section, choose the Assigned Objects tab.
The Assigned Objects tab page opens.
Choose Expression from the Type field and choose Create Object.
In the Object Creation dialog box that appears, enter the following data:
Name
Short Text
Text
Choose Create & Navigate To Object .
Note
If you choose Create button, the function call expression appears under the Assigned Objects tab.
Assign result data object.
You can assign an existing data object or create a new data object.
Select an Existing Data Object
Choose
(Graphical Access).
In the context menu, choose
In the Object Query dialog box that appears, select the data object and choose Select.
Create a New Data Object
Choose
(Graphical Access).
In the context menu, choose Create Result Data Object....
In the Object Creation dialog box that appears, create the data object.
More information: Creating Data Objects
Assign target function to the expression.
You can create a new function or use an existing function as the target function.
Create a New Function
Choose
(Graphical Access).
In the context menu, choose Create Function...
In the Object Creation dialog box that appears, create the function.
More information: Creating a Function
Assign top expression to the function.
More information: Assigning Top Expression
Assign context and result to the function.
More information: Assigning Context and Result
Select an Existing Function
Choose
(Graphical Access).
In the context menu, choose .
In the Object Query dialog box that appears, select the function and choose Select.
The context data object of the target function appears under the Target Function Context Data Object in the Mapping section.

Map the context objects between the source expression and the target function.
You can choose a data object or an expression.
Choose an Existing Data Object
Choose
(Graphical Access) under the Source Context Data Object/Expression column.
In the context menu, choose .
In the Context Query dialog box that appears, select the data object and choose Select.
The context data object appears under Target Function Context Data Object in the Mapping section.
Choose an Existing Expression
Choose
(Graphical Access).
In the context menu, choose .
In the Object Query dialog box that appears, select the expression and choose Select.
The context expression appears under Target Function Context Data Object in the Mapping section.
Save the expression.