VBS in Goals Center - Modify a standard field to convert it from free text to drop-down menu

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Hello experts,

can you give me some inputs on the possibility of converting a standard field from a free text box to a drop down menu with an array of values?
I thought this could be done through Business Rules creating an advanced rule but even after modifying the code on Javascript, it seems impossible.
The field is the Goal Name in a specific goal plan: the condition I'm trying to include statest the following - if the goal plan id is the one I'm passing, then the Goal Name field should be displayed as a set of values.