question about interaction between own state information...

hi question about interaction between own state information... my problem is very simple: i have an object with a class-member-function which writes a file of about 2MB. the duration of this function is quite long. thats why i'd like to have display informations in a pop-up. for that reason i made a member-variable for getting a counter and set the object into a registerd session. the running writefunction will now increase the counter every time it wirtes information to the file. on the other hand, the pop-up should access the same session and read the counter-variable on the object with the running wirtefunction. my problem: i cannot access the session on the pop-up WHILE the writefile function is running. that writefile function is locking the session in some way. that seems logical for me. now, how can solve my problem? my main-window should be able to interact with its pop-up-window. i would like to send state information from a running function on the main-window to its pop-up-window. this is refreshing automatically. Thanx for every hint or answer Regards, Jürg Zgraggen