Adding a text

do you mean something like this... =IF(C2="wer_dane","WER_DANE;POBR_DANE",C2)

EDIT: this would also do the trick... =IF(C2="wer_dane",C2&";POBR_DANE",C2)

Why not simply SUBSTITUTE?

=SUBSTITUTE(C2,"WER_DANE","WER_DANE;POBR_DANE")

how about this... =IFERROR(IF(RIGHT(C2,SEARCH(";wer_dane",C2)-2)=";wer_dane",C2&";POBR_DANE"),C2)

Slightly simpler:
=IF(ISERROR(SEARCH("WER_DANE", C2)),C2,C2&";POBR_DANE")

In plain English: search in C2 for "WER_DANE". If not found ("ISERROR"), just put the existing contents of C2 in this cell. Otherwise, put in this cell the existing C2, with ";POBR_DANE" added at the end.

Note that none of these suggested solutions actually change what's in Column C: they just show the result in whatever column you put the formula in. To make the result appear right next to the names as shown in your sample, you'd put the formula in Col D and hide Column C.

I'm looking at F4 and G4 and the formula I gave you in post #5 isn't the formula you have in column G. I pasted my formula in again and it appears to give you what you want. I pasted my formula in cells F7, F8 and F9 and did a simple equal test. If the results you want are in F3, F4 and F5 my formula appears to give you what you want. See your sheet attached.

I'm assuming that this "SZUKAJ.TEKST" either means right or search that are in the formula. The item you are looking for "WER_DANE" appears at different locations in your sheet so looking left wasn't a good option. So I used search. Search for ";WER_DANE" returned 11 for your first location it found it (cell C2) So simple =Search(";WER_DANE",C2) will return 11. Then going in from the right since it appears to be the last part of the cell you want, if you add the Right to that formula, ";WER_DANE" is 9 in length. 11 - 9 is 2, so I had to go back 2 spaces to pull out the ";WER_DANE" part. Since that is what I'm looking for in the if function that is what I needed it to find.
Hope that makes sense. If not, try sections of the formula building it from the Search out and you'll see.

You could use the joker sign * in the search formula.

show the file and add manualy the expected result in your file.

Per your post #11, in my formula it doesn't matter how many numbers in it has to go to find the ";WER_DANE" as long as that is the last part it is looking for. So in other words, it has to be the part at the far right of the cell. So it could begin in the 25th position and the formula would still work as long as it is the last part of the cell.

if ";WER_DANE" is always on the right, use this in instead... =IF(RIGHT(C2,9)=";wer_dane",C2&";POBR_DANE",C2)
this will work.

see the attached sheet with the formula I posted in post #17.

maybe like this, see the green cell.

You're welcome! And if that solves your issue please don't forget to mark the post as solved using the thread tools dropdown at the top of the post. And if you are so inclined you can click on "* Add Reputation" at the bottom of my post to add to my reputation, it is how we advance on this forum.