Prefill checkboxes field based on appended string field?

Is it possible to prefill a checkboxes field based on an appended string field? For example:

• The string field items contains multiple appended items: item1; item2; item3
• Is it then possible to prefill a checkboxes field like this:

items:

✓ item1

✓ item2

✓ item3

x item4

Right now we're using a solution where we use a separate boolean field for each item, but this clutters our database. We would like to keep the amount of custom fields to a minimum.

Hope someone can help.