In IFS Cloud you should be able to use a Workflow for this.

In IFS Applications 10 the options are either 1) customization (code change) or 2) an Online SQL type event action, that can be used to pop up an information box after you have saved the data, but it doesn’t work in all screens. (It’s a matter of trial and error.)

Sample block:

BEGIN
   Client_SYS.Add_Info('PurchaseReqLine', 'MY1STMSG: Do not forget to add purchase group.');
END;

To make sure the popup presents neatly, the first parameter should be a logical unit name (but using 'Dummy' will work perfectly fine), and the second should start with a unique tag (per LU) in uppercase immediately followed by a colon (because IFS will look for translations, but we don’t need that).