regular expression

Question

Hi can any of you help me creating a regular ecpression? 

the expression is used to validate userinput from a textfield in a asp.net website

it should validate a username: roules for the username is that starts with pc or lc, and afterthat its 4 to 8 numbers like:

pc12345678 or lc12345678

can any of you create a regular expression for me? :)