Find Markers in bank

Hey, i want to find markers in a bank.
Can i find this with

System.IntPtr userData;
soundData.getUserData(out userData);

and what is the callback type of

?? test = (??)Marshal.PtrToStructure(userData, typeof(??));

getUserData will only get information that you (the user) has manually added to it.

Retrieves a user value associated with this object.

What is it that you are trying to achieve?