InfoPath Dev

OK I will do my best to explain the problem I am having. I am trying to create an Infopath form that we can fill out for offsite tapes. I created a database with child tables as follows

DB Backup
      Tables
          DBO.BACKUP
          DBO.TAPES

The backup table has the following:
BackupDate (Prim KEY)
SealDate
SecuritySeal
SealEMP1 (Prim Key)
SealEmp2 (Prim Key)
Notes
UnsealEMP1 (Prim Key)
UnsealEMP2 (Prim Key)

Tapes table has the following:
BackupDate (Prim Key)
BackupSet
BarcodeLabel
SealEMP1 (Prim Key)
SealEmp2 (Prim Key)
UnsealEMP1 (Prim Key)
UnsealEMP2 (Prim Key)

I have the BACKUP table set as a Section and the TAPES table set as a Repeating Table. I have the table repeating like 11 times on the form which is the current number of offsite tapes we have. What they would like to have done on the form is this. The Backupset field to be pre populated with the backup set name for each tape. So if the first set of tapes was for a file server backup they would want the backup set to already have "FS backup Tape 1", FS Backup Tape 2", etc already there. The BackupDate, Seal EMP1, SealEMP2, UnsealEMP1, UnsealEMP2, on the repeating table to contain the same information as what is listed in the Backup table Section of the form.

The problem is that I don't know how to get the backupset names to prepopulate into the repeating section and when you will out the backupdate, sealemp1, etc part of the form it only copies to the first part of the repeating table. I had sugested doing a drop down list for the Backup set but the concern is that there is a chance to select the wrong set name for a tape. any Ideas you can think of would be great. If you need further information I can try to explain further.

I've attached a sample that uses preceding-sibling to do what you want, I believe. Right click the link in the header of this post, and select save as to save the form locally. Then right click your local copy and select design to open in design mode. Preview to see the auto populated info, and add additional rows to see more. Hope that helps!

That is real cool thanks. Now my question is when I am putting in the code I'm getting an error stating:

 "../preceding-sibling::my:backup/my:tapes/backupset" does not point to a valid location path of a field or group.

Here is the code I am using.

concat("FS Backup Tape ", count(../preceding-sibling::my:Tapes/my:backupset) + 1)

I've changed my DB to look like this.
Backup
     BackupDate
     SealDate
     SecuritySeal
     SealEMP1
     SealEMP2
     Notes
     UnsealEMP1
     UnsealEMP2
     Tapes
          BackupSet
          BarcodeLabel

Also the reason I am doing a single field for the barcode label is so I can search the DB for a barcode of a tape and it will find the tape reguardless of what backupset it is from. We currently have 4 different backup sets that run everyday. So my other question for you would be could I create multiple repeating sections in my form and set each repeating section up for a different backup set using the formula you sent, but still only use the 2 fields in my DB for Backupset and BarcodeLabel to list the tapes.

Thanks again for your reply.

I figured out one issue. the datatype for the textbox field that is bound to BACKUPSET in the DB is currently set to SimpleText. But it's greyed out and I can't change it to match what you have in your example.