Swap Form Input Fields Contents?

I have one form on a page with 'n' text input fields grouped in blocks of the same input fields. Something like this:

<div id="block1">
name_1
lastname_1
address_1
phone_1
...
</div>
<div id="block2">
name_2
lastname_2
address_2
phone_2
...
</div>
...

The number of fields for each block varies because the page is constructed by a server function. What I want to implement is move up and a move down buttons on each block to move what the user has entered in say, block 4, to block 3 (and move the block 3 contents to block 4). And the contrary too.