DOS.exe calls from C's system();

I may have forgotten this but it should be a snap for others. I had to split a program up into 4  and call them by system("prog?.exe"), etc. Now when I run prog3.exe then call system("prog1.exe), and later within prog3.exe then call system ("prog2.exe"), OK. However, with a prog4.exe, if I call system("prog3.exe") and then call system("prog1.exe") or system("prog2.exe") as above, it fails. In other words. I can't have more than 1 nested system call within a system call?  I split the program up but now can't link them together. Should I link the prog?.obj in Visual C++ DOS.exe of the compiled C programs? I tried a few batch files (bat.) and call *.bat's but too rusty???