Instruction of assembly language

[hatsoff]

What is the instruction to invert content of a register?

I'm using these two instructions to do a AND logical operation b/w two registers and store its result in 3rd seprate register:
have a look!

and ax, dx ; AND operation b/w ax and dx register and storing its result in ax first then ->

mov bx, ax ; storing result in bx

Cant it happen simultanously (Imean and operation and storing result in seprate register) in one instruction?
I'm using NASM assembler and AFD debugger.

Thanks

[MG&TL]

I'm not going to give an answer in code, (partially because I'm not comfortable with the dialect of assembly I know, let alone NASM) but if you XOR the bits with 1, it'll invert them. http://en.wikipedia.org/wiki/Bitwise_operation#XOR

[schragge]

I'd be surprised if NASM didn't have the NOT instruction.
Edit Sorry, I didn't read your question right. If you want to store the result of inversion elsewhere then MG&TL is right: just use XOR.