With an interactive session on the AS400, the Enter key must be used to initiate the next action to be taken. So, if you put a ‘1’ in a Subfile Select field nothing will happen until you depress the ENTER key.
Now if you are asking how to get data from a subfile screen to a different format on the display, that is a different question..
If you have the same field names in the record format as you do in the single record format, when you do a READC to read the subfile record than the data in the display will populate properly.
Usually when you have a subfile, you do not have all the data elements in the subfile that you want to display on the single record screen. All you need to do is tio put those fields in the subfile amd make them HIDDEN fields by using H as the use code.
If you field names in the database file are the same as what in used in the DSPF, you may want to the the PREFIX keywork on the F specs.
HTH, if you need more, just let us know.