Add Record Pop-Up - Combo Box Requery

Hi - My first time here, and I am fairly new to Access, but getting on OK. So as ever, be kind.

I have spent several hours reading this forum and learnt a few things, and been completely confused by other things. My Job is IT but Software, Networks etc configuration rather than programming.

I am trying to help a charity out by building a database for their Sportsday.

I have a Parent Form Called Team, with Sub forms in Tabs for Team Details, Competitors etc.

In the Team Details, They can Choose the Hospital and Team Manager.

I have a Combo box with a lookup query, which looks up the Manager. However, rather than just display a last name, I have changed the SQL behind the (Properties - Data - Row Source), so that I get a concatenation of the Surname and First name:

SELECT tblCompetitor.CompetitorID, [surname] & " " & [Firstname] AS Fullname FROM tblCompetitor ORDER BY tblCompetitor.Surname;

All Works fine

I know I can use a "Not In the List" command, but initially they want a button to open an Add Manager Form.

No Problem except when I close and try to enter the New Managers Details in the Combo Box and requery.

I have a button to close the Add Manager Form and requery the Manager Combo in the originating Form

Private Sub CloseCompetitorsEditPopUp_Click()
On Error GoTo Err_CloseCompetitorsEditPopUp_Click

Forms![frmTeam]![ChildTransplantTeam].Form![Manager] = Me.CompetitorID
(the Manager field is a lookup from the Competitor table)
Forms![frmTeam]![ChildTransplantTeam].Form![Manager].Requery
DoCmd.Close

Exit_CloseCompetitorsEditPopUp_Click:
Exit Sub

Err_CloseCompetitorsEditPopUp_Click:
MsgBox Err.Description
Resume Exit_CloseCompetitorsEditPopUp_Click

End Sub

This code works fine if I just use the Managers Surname as the Data Field, but leaves a blank field in the Combo Box if I am displaying concatenation, until I do some sort of refresh.

Any Ideas if I can do this seamlesly as it is driving me potty.