How can I merge 2 dcd trajectory files?

So I am in a situation where my 2 chains (2 proteins) from the same simulation are separately in 2 DCD files each having 2000 frames. I wanted to merge these 2 DCD files into single DCD file (which will have total 2000 frames) containing both chains. I know this might be possible in VMD. Can someone help me?

NOTE : I am not talking about concatenating DCD files (which is done using catdcd)