In other words, I want to convert (id_witness):

518
501
500
518
504
534
544
556
547.1799

to (id_Qs):

518.1799
501.1799
500.1799
518.1799
504.1799
534.1799
544.1799
556.1799
547.1799

First of all, a return-separated list of numbers is not a number, and the correct type of field to hold such list is Text. Filemaker is pretty tolerant when it comes to field types (and data types in general) but you may run into unexpected consequences of such mismatch.

Now, assuming that the return-separated list does not have a trailing return, you could do the required conversion quite simply as:

Substitute ( id_witness ; ¶ ;  ".1799¶" ) & ".1799"

(I am also assuming that the "547.1799" entry in the source list is actually "547".)

 

Thank you sooooo much!