The PROC REPORT documentation talks about how PROC REPORT processes from left to right. So if you want to have this computation for newvar:
newvar = var2.sum + var4.sum;
Then you have to place newvar3 AFTER var4:
column var1 var2 newvar var4; < ---- WRONG
column var1 var2 var4 newvar; < --- RIGHT
This same concept applies to a COMPUTE block...if you have this:
column grpvar var1 var2 var4 newvar ;
And, if grpvar is a NOPRINT variable, then the variable you need to change at the summary line is the VAR1 variable "slot" or cell.
For more help with PROC REPORT syntax and making the changes you want, you might consider contacting Tech Support.