No answers despite several views, so I'll chime in with something else since I have no experience with ds' and I've never heard of Access having such capability. I don't get what the issue is with respect to multiple fields for this, and even if you could link Access to the source, you might find it's stored in multiple fields anyway. If not, to store 3 parts of a signature in a db as 1 field doesn't follow normalization practices IMHO, and I wouldn't do it unless absolutely necessary.
If you could be content with capturing info like the user name, date of a change and even the pc they made the change on, then many of us here could likely help with that.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.