Only names of single form fields can be used with a BEFORE or AFTER clause. The name of a field is defined in the ATTRIBUTES section of the form definition; it is often the same as the name of a database column. Here are example lines from an ATTRIBUTES section:
atag = customer.customer_num,noentry; tag2 = formonly.total,format="#######.##";
The names of these fields are customer_num and total, respectively.
In the 4GL statement in question, you have written a name prefixed with another name and a dot. That syntax is used for specifying components of screen records or screen arrays, or database columns of the same name in different tables, but it is not appropriate here.