SPSS syntax - ANOVA simple effects analyses

I have conducted several ANOVAs over the course of my research but I do not know how to write the script to perform simple effects analyses on the significant interactions. One example is:
"A 2x3 mixed-model ANOVA was performed with stimulus type (most versus least-selected) as the within- subjects variables, and age group (60-69, 70-79 and 80-89) as the between-subjects variables, and percentage of times the most-selected or least-selected elements were selected as the dependent measure. This analysis showed that there was a significant main effect for stimulus type [F (1, 57) = 352.919, p= 0.000], a significant main effect for age group [F (2, 57) = 8.037, p=.001] and a significant interaction effect for the two variables [F (2, 57) = 6.796, p=.002]. "
I would greatly appreciate any help someone could give me.