Append From A Text Box To Only Blank Field In Saved Record In A Table

I have designed a database that has two forms as inputs to a table. The first form is a checklist and when it is completed it saves all fields except the ManagerID field. I then use the blank ManagerID, clientID and Date to pull onto a form for the manager to complete. On completion I want the ManagerID to save into the current records so they do not show up in the manager checklist forms and I then have a complete record. I have been searching online and cant seem to see how the best avenue is. I have an append query, see below

Code:
INSERT INTO ChecklistResults ( ManagerID )
SELECT ChecklistResults.ManagerID, ChecklistResults.ClientID, ChecklistResults.DateCompleted
FROM ChecklistResults
WHERE (((ChecklistResults.ClientID)=[Forms]![TeamLeader]![ComClientNotFin]) AND ((ChecklistResults.DateCompleted)=[Forms]![TeamLeader]![ComDateSelect]));

Code:
Private Sub CmdAppend_Click()
Dim dbsNorthwind As dao.Database
Dim rstAmend As dao.Recordset
Dim qdfAmend As dao.QueryDef

[code]...