Wrong data in text files

I have a problem and i hope to find here an answer. I'm running uft with some data. One of my lines of code opens window Data stream and another code take all the data there by copying it(it copy the data that on the screen->output) and save it in a txt file(no1). At the same time the same code running in another environment (2 environments running at the same time) and also save data in another txt file(no2). The problem is that some txt files containing data from second environment txt files (txt file no1 contains data from txt file no2). Any suggestions?