Cheat Engine

[Popinman32]

How would I go about finding a specific type of structure in a program's memory as it's created (therefore finding the code that generates it)?

[Dark Byte]

Place a hook at all memory allocation routines, and all internal allocation routines as well.
Then each time a block is allocated start single stepping until the first few bytes have been written to the allocated memory block. That should be enough to identify if it's the structure is that you want or not. If it is, you're in the function that creates it.
Now just find where the start of the function is (stacktrace) and you're done

alternatively, perhaps you might find a pointer to the class definition (vtable like thingy) and find the constructor method of the class. If you place a hook on the constructor you might be able to find the caller then as well.

It may take several tries till you've found the constructor though as it's not always the first method, and there can be multiple constructors