Oh, that's a bit different.

Assume that what is in the listbox is moved into a variable called st1.

Path.GetFileName(st1) will return Library.lib.
It looks like textbox1 can be st1
It looks like textbox2 could be simply "u:\converted_files\job\ab_" & st1
For textbox3, you could use "u:\converted_files\job\ab_" & st2

where st2 = st1.substring(0,st1.length - st1.IndexOf(".")) & ".log"

I may be off on the second argument of substring, I may have the subtraction off by one. I'd want to test it before I used it.