How can I get version of release before updating application?

How can I get version of release before updating application?

I am beginner in android programming, so please help me to find out in
some questions and sorry for my English. I develop application on eclipse
for android. And I want to develop module of load update file from
website. I know how can I get update file, load and launch it from
programm code (example of code you can see by this link Android: install
.apk programmatically). But before I want to get version of release of
update file. And I don't know how I can do it. May be somebody developed
the same module and can give me advise.