May you please provide guidance on how I can use PROC GLIMMIX to analyze the results of a 4 x 3 factorial experiment for a continuous variable measured at 4 equally spaced intervals.
First, your title talks about repeated measures, but then your text does not. It is always a good idea to have the title and text agree with each other. So a clarification would be helpful.
ANOVA, or Analysis Of Variance, is used to compare the averages or means of two or more populations to better understand how they differ. Watch this tutorial for more.