I was just thinking of using a straight link.
<a href="{path=form/page_1/{entry_id}">Prev</a>
Or something like that. I suppose that the PREV button wouldn’t submit the data though. I knew we’d used PREV buttons somehwere, but when I went to check it out, it had the same limitation.
<a href="{path='client/payment/{segment_3}'}" class="prev_bttn">Previous</a>
<button id="checkout_next" class="next_bttn">Next</button>
{/exp:cartthrob:checkout_form}
I suppose you could use jquery to change the return value on the fly when the previous button is pressed. You could have a prev button change the return value, AND submit the form after that.
<input type="hidden" name="return_url" value="safecracker/ENTRY_ID" />
<input type="hidden" name="return" value="safecracker/ENTRY_ID" />