Simulating Drug Entry in Protein and binding?
This is a tough topic, have a look at the following references and see, if they can help you:


Structural modelling and dynamics of proteins for insights into drug
interactions.
Ligand entry pathways in the ligand binding domain of PPARγ receptor
Pathway and mechanism of drug binding to G-protein-coupled receptors
Molecular Dynamic Simulation and Inhibitor Prediction of Cysteine
Synthase Structured Model as a Potential Drug Target for
Trichomoniasis