There is a demonstration for a set of grouped box plots using the Box Command on YouTube:
https://youtu.be/OWmiBjqVaCw?si=zhwUcjNCBF9IrWKg
This requires that you have the raw data. So you don’t need to have the values computed; DataGraph can do that for you. However, you mentioned that you already have the summary stats calculated. In general, we recommend using the raw data to modify how you slice and dice the data in DataGraph, but if you want to use your calculations, you can use the Bar command to construct a Box Plot. There is an example file available that shows how.
You would need to modify the example file and could set up something like this …
Again, if you have the raw data, that would be what we recommend, but if you want to construct the bars, hopefully, this example file will get you started. Let us know any other follow-up questions/issues you have.