How to write a contrast statement in proc mixed

[N2Nutrition]

Hi, I am having a most difficult time writing contrast/estimate statements and hope someone can help me with my error.
Background: I want to learn if the means of (pretrt=2 stain=5) and (pretrt=3 and stain =2) are equal.

This is how I wrote the statement.

Contrast 'p2s5 vs p3s2' intercept 0 pretrt 0 1 -1 stain 0 -1 0 0 1 pretrt*stain 0 0 0 0 0 0 0 0 0 1 0 1 0 0 0

Thank you. I am consistently getting wrong answers when I write these statements.
I guess it is good I'm consistent....

[natapata]

maybe:

Contrast 'p2s5 vs p3s2' intercept 0 pretrt 0 1 -1 stain 0 -1 0 0 1 pretrt*stain 0 0 0 0 0 0 0 0 0 1 0 -1 0 0 0
?