Measuring the memory used by a graph

I code in C++ on Windows, using codeblocks with g++. I have a graph defined as follow (using boost):

Code:

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struct NodeData{ /*...*/ };
struct EdgeData{ /*...*/ };
typedef adjacency_list<setS, setS, undirectedS, NodeData, EdgeData> MyGraph;
MyGraph G;

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This graph is updated iteratively (by adding/deleting some edges/vertices). At each iteration, I want to evaluate the memory space occupied by this graph G. How can I do that ? And what if I compute V = "the size of NodeData" and E = "the size of EdgeData" and at each iteration the memory used by the graph will be proportional to: nbr_vertices * V + nbr_edges * E ?