does anybody have a fdtd code for the subgridding?

these days, i am working for the subgridding of fdtd, but i find there is a complex work for programming, does does anybody have a fdtd code for the subgridding? do you want to give me a help about these questions, please do me a favor! my email is xinliutj@gmail.com, i also want to discuss some questions with you if you want.