Force the actual value field of a goal

Content

Hello,

we would like to force the field of the actual value of a goal. In detail in the measurement section of the goal we would like to force what it is possible to insert in the field actual value. The desired is to have the possibility to insert into this field only the value 80, 100 or 120 in order that it is not possible for the manager to insert a different value.Is this possible to do it with a customization building an Expression languagge for this field?

Thank you,

Giulia