You haven't indicated what you need to do with this new field information but a scrript isn't necessary. Create a calculation (result is TEXT) with:
NameField & " " & SurNameField & " " & AgeField
... it is known as concatenation (combining several fields together with a space between. If you want the calculation to be a multiline, it would be:
NameField & ¶ & SurNameField & ¶ & AgeField
UPDATE: depending upon why you need this information, you might always want to consider using a merge field which would look something like:
<<NameField>> <<SurNameField>> <<AgeField>> (there is a space manually placed between each inserted merge field.
I have to add this information to an existing container field that already contains some text. The idea would be to activate the script using a button, so that when the information in the fields becomes outdated, it can be manually moved to that other field that is some kind of a log.
Why are you using a container field to hold any old data? I suggest you use a regular text field so it can be easily searched if you want to find an old entry.
Here is an example of adding a line to an audit log text field called AuditLog (placing the most recent at the top). It includes the current date but you can omit that if you wish:
Get ( CurrentDate ) & ": " & NameField & " " & SurNameField & " " & AgeField & ¶ & AuditLog
... when you click the button, the latest entry will appear at the top.
Sorry, I actually realized it is already a text field.
The first solution works very well, I only added the name of the target field to the calculation so that it adds it all up to the existing text, like this:
TargetField & " " & NameField & " " & SurNameField & " " & AgeField
The audit log idea might also turn useful. Thanks a lot for your help!