Conditional syntax is easiest to explain with an example.
DO IF (GroupNumber=1 and Location=1).
ELSE IF (GroupNumber=1 and Location=2).
ELSE IF (GroupNumber=2 and Location=1).
COMPUTE Condition = 3.
ELSE IF (GroupNumber=2 and Location=2).
Condition 1 "Control Group in Cuba" 2 "Control Group in Miami" 3 "Experimental Group in Cuba" 4 "Experimental Group in Miami".