Script to find the Next cell and Previous cell

How to find the Next cell
proc name {
set n [get_cells -of_objects [get_pins -of_objects [get_nets -of_objects [get_pins -of_objects $name -filter "direction==out"]] -filter "direction==in"]]
}

How to find the Previous cell
proc name {
set n [get_cells -of_objects [get_pins -of_objects [get_nets -of_objects [get_pins -of_objects $name -filter "direction==in"]] -filter "direction==out"]]
}