How to toggle file names in Windows 7 command-line

I want to toggle the names of two files, using a batch file (Windows 7 command-line). I wrote the following code, but its not working.

IF EXIST test12.txt
rename test.txt test23.txt
rename test12.txt test.txt

Could someone help me correct this code?

Thanks.

EDIT: When I run from the command line, it says "The syntax of th开发者_如何学Ce command is incorrect". What is the syntax then? Is this only for checking the existence of directories?

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Not sure if this is what you are asking. Perhaps your IF clause isn't correct. By using () the code should improve.

IF EXIST test12.txt (
    rename test.txt test23.txt
    rename test12.txt test.txt
)