Update node multi value field programatically
I think I found a solution.  I used hook_node_presave to check if a value was set, ad if not to set it to -1 for the 28 fields I have.  Maybe not the most elegant (I would love to hear if there is a more drupally way to do this) but it works.

function mymodule_node_presave($node) {
if ($node-&gt;type == 'mynodetype') {
for ($i = 0; $i &lt; 29; $i++) {
if (!isset($node-&gt;field_scores_a['und'][$i]['value'])) {
 $node-&gt;field_scores_a['und'][$i]['value'] = -1;
}
if (!isset($node-&gt;field_scores_b['und'][$i]['value'])) {
 $node-&gt;field_scores_b['und'][$i]['value'] = -1;
}
if (!isset($node-&gt;field_scores_c['und'][$i]['value'])) {
  $node-&gt;field_scores_c['und'][$i]['value'] = -1;
}
}
}
}