Contrats coding

#1
I have a data set with eight conditions. Am trying to code a contrast to test the difference between condition 1 and condition 2 compared to the average difference between the conditions 3 and 4, 5 and 6, 7 and 8.

Am doing this in SPSS with the following syntax:

GLM DV BY COND
/CONTRAST(COND)=SPECIAL (3 -3 1 -1 1 -1 1 -1)
/METHOD=SSTYPE(3)
/INTERCEPT=INCLUDE
/CRITERIA=ALPHA(.05)
/DESIGN= COND.

I get some result but not confident am doing it right. Does the statement 3 -3 1 -1 1 -1 1 -1 actually test what am trying to test? Any contrast coding experts out there?

Thanks for any tips and help!

/Tarje