How I Force delete a file?

Hi, I made a program to gets off the internet a picture that the server I get it from updates like every 3 seconds ..(its PNG) which shows that status of a online radio station (Song played, # of listeners, etc.) In my program I have a refresh button to resynchronize with the server on the internet, but insted my program gets the picture from the temporary internet files. I went in that folder and I saw the picture there but I cant delete while my pgoram is running. So I just ran disk cleanup while my program was running, clicked refresh and it worked. So I have to find out how to force delete those pictures to make my program refresh from the server not from my computer.

I tired:
KILL {filename}