Query unique records, except for one field

[bigalpha]

The title is probably confusing and/or weird because I couldn't figure out how to say it.

I have a report that I'm going to use to make labels for a folder; it's a list of Manifests under a Delivery Order.

Here's the breakdown of data hierarchy:
One Delivery Order can have multiple Manifests which can have multiple wastes and each waste is assigned a letter code: N, H, U.

I have the report outputting perfectly except for this letter code, which I'd like to stick into a text box on the report, like so:

DO, Manifest #, Letter Code
1142, 1, H, N, U
1142, 2, U
1142, 3, H, U

Because each manifest can have multiple wastes, like so:
Manifest 1
1) Used Oil, N
2) Batteries, U
3) Acetone, H
4) Acid, H

I don't know how to make my letter code on my report say H, N, U instead of H, H, N, U.

Here's my SQL for the underlying query:

SELECT DISTINCT tblDeliveryOrders.DeliveryOrderNum, tblManifestData.Manifestnum, tblTSDF.TsdfName, tblCertifiedmail.certifiedmailnumber, tblManifestData.REMOVEDdate, tblManifestData.ManifestType, IIf([OriginalManifestReceived]=#1/1/1900#,"N/A",IIf([OriginalManifestReceived]=#1/1/2100#,"Yes",[originalmanifestreceived])) AS [Orig Man], IIf([MailedDate]=#1/1/1900#,"N/A",[maileddate]) AS [Mailed Date], IIf([certifiedmailnumber]="0","N/A",[certifiedmailnumber]) AS [Certified Mail Num], DatePart("q",[removeddate]) AS Quarter
FROM tblDeliveryOrders INNER JOIN (tblCertifiedmail RIGHT JOIN ((tblTSDF INNER JOIN tblManifestData ON tblTSDF.TsdfIDPK = tblManifestData.TsdfIDFK) INNER JOIN CurrentCY ON tblManifestData.ManifestDataIDPK = CurrentCY.ManifestDataIDFK) ON tblCertifiedmail.CertifiedMailNumberIDPK = tblManifestData.CertifiedMailNumberIDFK) ON tblDeliveryOrders.DoIDPK = CurrentCY.DeliveryOrderNumberIDFK
WHERE (((tblDeliveryOrders.DeliveryOrderNum)=[forms]![frmManifestFolderLabel].[txtDoNum]));