Welcome to the forum.
I'll answer the technical question as I interpret it. If I have misunderstood the question, don't hesitate to correct me.
When you have a recordset open, you can tentatively write a field that might be stored using recordsetname.fieldname = somevalue but that wouldn't be enough to commit the update. If you are using an UPDATE query, you can use syntax like UPDATE table SET field = value WHERE ... (and you hope that your WHERE clause is specific to the record or records you wanted to update.
However, somehow I get that your problem is more basic even that that. You didn't specify whether your question was in VBA context or SQL context, and the answers for those two cases usually are quite different.