To add a function to a codeunit, use the following procedure.
To add a function
- Select the C/AL Editor, choose View, and then choose C/AL Globals.  Note Note- For more information about how to open the C/AL Editor, see How to: Modify an Existing Codeunit. 
- In the C/AL Globals window, choose the Functions tab. 
- Enter a name for each function that you want to add. 
- Choose Locals to define the parameters, return value, local variables, and text constants in the C/AL Locals window. 
- In the C/AL Locals window, choose the Parameters tab and specify the calling method, name, and data type of each parameter. You can also specify a subtype and a length, but this is optional. - To specify the calling method of a parameter, either select or clear the Var check box. If you select the Var check box, then the parameter is passed by reference rather than by value. The value of a variable can only be changed by a function when it is passed to the function by reference. When the parameter is not specified as Var, only a copy of the variable is passed to the function. If the function changes that value, the change only affects the copy and not the variable itself. - If the type that you select corresponds to an application object, then you must also add a subtype, that is, the name of a specific object in the database. If you select Text or Code data types, then you must define a length. The default length is 10 characters for Code and 30 characters for Text. 
- In the C/AL Locals window, choose the Return Value tab and specify the return value for your new function. Enter a name for the return value and select a data type from the drop-down list. If the data type is Text or Code, then you can also select a length. 
- In the C/AL Locals window, choose the Variables tab and define local variables. - For each local variable, you must enter a name and select a data type. If the data type that you select corresponds to an application object, then you must also add a subtype, that is, the name of a specific object in the database. If you select Text or Code data types, then you must define a length for the variable. The default length is 10 characters for Code and 30 characters for Text. 
- In the C/AL Locals window, choose the Text Constants tab and define text constants for the function. 





