Update TXT List using external software

Hi, 

I am new using SIEMENS. I am programming a KTP 400 Comfort. linked to a S7-1200. 

I would like to ask you how to do a solution I normally used in OMRON. 
There, I use an "indirect label" to index the line of a TXT file I want to show in a label of a button or indicator. This is similar to the "list of text" in TIA Portal. However, in OMRON I found the way to updated automatically the TXT file in the HMI using a computer but not using the software of OMRON. 

So, I would like to know how to do something similar using this SIEMENS HMI. I would like to show a label whose text changes according to the value of an index. However I would like to be able to change the file where the index points (TXT, CSV, etc) but not using TIA Portal. I would program a software to send the updated file automatically under FTP, or under the protocol you suggest me. 

Thank you very much.