Model Builder - Calculate Field (Area)

Hello,

I'm a totally newbie to Python and have problems to calculate the area of an input feature in my model (model builder).
I use the "Calculate Value" function to calculate the area (in square kilometers or meters) of an input feature (either a raster or a vector feature - should both work?).

I found out that it works like that: !shape.area@squarekilometers!

I have my forumla in the expression block like x/200 and want to calculate the area of myFeature represented by x.
My code block is the following: x = !myFeature.area@squarekilometers!
I also tried the following: x = !%myFeature%.area@squarekilometers!

But I always get an error (ERROR 000989 Python syntax error: Parsing error SyntaxError: invalid syntax (line 1)).

Does anyone know what I'm doing wrong?

Thank you!