single button to call multiple forrms

Question

Hello,
I have button on my main form..
I have panel on form..
I have several other forms.. say accounting1, accounting 2,accounting3

On button click I want to call a particular form(accounting1) in panel..
now on button click I want to call accounting 2 in panel..
Problem is I am using single button to call forms

How to maintain this sequence on single button.. Can anyone give me code..
Its urgent