Change a lookup based on Sheet Set Manager custom property

Hello,
I would like to change a lookup selected value so it "matches" a custom property from the sheet set manager, for what i could comprehend on another post it can be done on regenerating the drawing. but i'm not too skilled at coding.
Let me give you an example to clarify
Lookup on a block has 4 options (call them A,B,C and D)
ssm has a custom property, named "Selection"
If i change "Selection" to A then the lookup should use the option A and so forth.
Please keep in mind i've not done any custom code for AutoCAD before so an explanation for a noob would be appreciated.
Thank you in advance.
Carlos