I found this line code in the script "System:SpellCheck", sub named "AddDateTimeStampEx(Sender)"

Application.UserOptions.GetAsBoolean("UserDateTime", "CustomerService")

But i can't find how set the UserDateTime value in SalesLogix Client or Administrator.

Anyone can help me, pls!!

Not sure what you are trying to achieve.

This option is set by default to False (on the USEROPTIONDEF table).

Also, this option is used to determine if the User Name and Time Stamp are added automatically to Memo fields (e.g. Description and Resolution Text Boxes for Ticket Details, or Comments for a Ticket).

This value can be changed by the Admin for each user from the SalesLogix Windows Client by accessing Tools/Manage/Customer Service Options menu Item.
It could also be enabled so that each user modify their own options, and then they would access it via the Tools/Manage/Customer Service Default menu item.

On the Grid (for the Admin) the field is labeled "DateTime", on the Detail view (both for the Admin and the User) it is labeled "DateTime: Default Username/Time Stamp in Memo Fields".

Excellent contribution Raul!