Execute a bash function upon entering a directory
Aliases don't accept parameters. You should use a function. There's no need to execute it automatically every time a prompt is issued.
function cd () { builtin cd "$@" && myfunction; }The builtin keyword allows you to redefine a Bash builtin without creating a recursion. Quoting the parameter makes it work in case there are spaces in directory names.
The Bash docs say:
For almost every purpose, shell functions are preferred over aliases.