Is there a way to select just a single entry from a combined text summary field?

For example, I have a Parent table that uses a combined text summary field for Tracking #'s of shipping crates. I want to be able to have a formula field on the parent record that will take one of the tracking #'s from the combined text field (preferably the last value added) and use that in a URL formula field to plug into the UPS,etc. tracking page. 

It would be nice if the various shipping companies would take multiple comma-separated tracking numbers at once but some do and some don't so I need to limit it to just one. 

Note: I have a tracking button already on each child record but I have been instructed that we need to be able to track at least one of the tracking numbers (most of the time there is only one anyways) from the parent record. Also, the length of the individual values may vary depending on the carrier company so I can't use Right(), Left(), etc. with a static length. 

Example combined text field:                           {P2626, P3737, P9876}
Fomula field, needed value:                  P2626

The Summary Test field type leverages existing functionality as the multi select field. You can convert that to a text field and it will be a semi colon delimited string.

The formula below would give the first  of the maximum 25 Summary text elements, separated by a comma, which I suppose might work for many tracking websites. 

var text value = [my summary text field]);

List(",",
Trim(Part($value,1,";")),
Trim(Part($value,2,";")),
Trim(Part($value,3,";")),
Trim(Part($value,4,";")),
Trim(Part($value,5,";")),
Trim(Part($value,6,";")),
Trim(Part($value,7,";")),
Trim(Part($value,8,";")),
Trim(Part($value,9,";")),
Trim(Part($value,10,";")),
Trim(Part($value,11,";")),
Trim(Part($value,12,";")),
Trim(Part($value,13,";")),
Trim(Part($value,14,";")),
Trim(Part($value,15,";")),
Trim(Part($value,16,";")),
Trim(Part($value,17,";")),
Trim(Part($value,18,";")),
Trim(Part($value,19,";")),
Trim(Part($value,20,";"))
) 



or else you can just use the first Part to get the first entry.

Trim(Part($value,1,";"))

Thanks for the info