Checkbox stays checked in post preview?

[Boofo]

I'm not sure how to go about doing this but I want to have a checkbox stay checked in the post preview only if it is checked before the preview. Otherwise, I want to leave it unchecked. How would I go about setting the conditional up for something like that? The php code is in the newreply_form_start hook and the template code is in the newreply template, if that helps at all.

[HMBeaty]

Not sure if this would help at all, but here's a snippet of code from one of my modification that does something similar as far as keeping an option when going to a new page...
<input type="radio" name="positionapplying" value="{vb:raw pos2}"<vb:if condition="$vbgpc['positionapplying'] == $pos2"> Checked</vb:if> />&nbsp;{vb:raw pos2}

[Boofo]

Mine is a checkbox like the signature checkbox so that probably won't work.

But thank you for responding and trying. ;)