MapStruct : enrich mapping annotation to define custom mapper

Here is my context: I am using byteBuddy to dynamically generate a class that transform an object into another one based on a external configuration. I encountered some issues and I wanted to find an alternative that's how I discovered MapStruct.

So I tried to build simple mapper and I wanted to know if there is the possibility to customize the annotation to add transformation functions. For instance I would like to have:

@Mapping(
    source = "mySourceField", 
    sourceType = "String",
    target = "myTargetField",
    targetType = "Integer",
    transformation = {"toInteger", "toSquare"}
),

And on the mapper implementation I would have something like :

 public TypeDest toSiteCatTag(TypeSrc obj) {

    if ( obj == null ) {

        return null;
    }

    TypeDest objDest = new TypeDest();

    objDest.myTargetField = Formatter.toSquare(
        Formatter.toInteger(obj.mySourceField));

    return objDest;
}

If someone can help me to achieve that I would be grateful and it would save me a lot of time.

Thanks in advance.