You can post a value as many times you like, but your actual task is to pass values between pages/posts.
You have two approaches:
0) when the values are posted the first time, you put them in hidden fields in the second form - and making the view model to retrieve them
1) by using session: simply gather what you need in a session object
+1) You could use the tempdata but it is meant for limited scenarios, so I wouldn't.
+2) You could use also ajax but might be complicated on client side - but you could address this approach in a future project. There are several examples out there, like this:
http://www.asp.net/mvc/tutorials/mvc-music-store/mvc-music-store-part-8[
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I would use approach 1.