How to know where comes the input data of simulation block?

Hello, guys, I have a littel question about the simulink input data. Some special block like Intergrator, has output and update function, the state value comes from the output of I-Block, not from the Source-Input(usually Y_constant), I use the eventlistener to check the input and output data, but it's only the value, so my question is, how can we know the source block of the input value? Has Matlab APIs already gave?