Using Selective deletion with a filter from the TVARVC table

Hi Experts

I need to create variables in the table TVARVC but  accept empty values...for me this a big problem, because i need to create variables without empty values (common error user).

Is it possible? ... also i make a copy of the standard table TVARVC a Z table to enable the option "initial values​​", however when I save the variable accepts empty values​​.

I need to ensure that when a variable is created always assigned a value.

Any idea ??

Note: I attach files for clarity