This sort of thing is a large part of what i'm doing for my job right now. Now, you do need to know if the page you're accessing is javascript based or not. If it's not, then here's some example lines of code.

automated login
Code:
username = "Whatever"
password = "Something else"

dim ie as object
set ie = CreateObject("InternetExplorer.Application")

with ie

.visible = true
.navigate "www.mypage.com"

do while ie.busy: doevents: loop
do while ie.readystate <>4 :Doevents:loop
'put this code after each navigation to make sure the page is fully loaded before continuing

.document.all.item("name of login name text box").value = username
.document.all.item("name of password text box").value = password
.document.all.item("name of login button").click
do while ie.busy: doevents: loop
do while ie.readystate <>4 :Doevents:loop
Basically you just look for the name="Whatever" tags in the html for the fields you want to input to and then put them in the Item("") section of the above code.