Assigning treatments to blocks in a RCBD experiment using SPSS

I wish to use SPSS or excel (preferably SPSS) to help me randomly assign 12 treatments each to 4 blocks in a Randomized Complete Block Design experiment. I would like to receive help on how to go about this.

Thanks

I have not been able to do this on SPSS. I would like to receive directives or the code on how to go about this.