in excel there are function of POISSON, how can we use in access?

Here is what I came up with when I googled your question

http://answers.microsoft.com/en-us/o...cc77692?auth=1

i don't know how to add in access

You will have to be more specific in your request. Where are you trying to add. In a query? In a form? As a matter of principle, it you are thinking of trying to do this in a table, then you really need to understand that tables are for holding data - not manipulating data. Manipulations are performed in Queries and sometimes forms.