checkboxlist and gridview data change

I have a gridview and binds to access database table using SqldataSource and when I run my page I see all data from table in GridView.
I added a Checkboxlist and values for checkbox list item. what I want to do is when I check the value it refreshes the gridview and fetches data. this works for the first item I check in listbox and it fetches the data from table.
but if I select multiple items in the checkboxlist its not filtering.
ex (table below 2 columns)
Name, Age
joe  55
mike 35
john 33
My ChckboxList
Check1 value 55,
check2 value 35
check3 value 33
if i select check1 i get Joe 55 in gridview but if i check1 & 2 only check1 data shows up.
can someone guide me on getting this straight? or if any other method i should use?