I have application 'a' (vb6) and application 'b' (vb.net). What is the best way to call method in 'a' using 'b' source code? I mean 'a' is recording calling numbers and when particular number calls it should change application's 'b' panel text (name). Yes, app 'a' could save all calling numbers to text file and 'b' could check for that particular number every one second or so, but it would be not efficient at all. Any ideas?