That's not going to work how you think.

I would suggest you update the catalog (you do have a catalog for this specific client, right?) with the client provided weights. Alternatively, you could work from a database and backfill the weight with some lookup queries or manually with a bit of cut-and-paste. Either way, there's already a field for weight and it's expected to be used as a weight. Trying to hack a description field as weight can cause some problems down the road - it still reads as "Short Description", so what's that number? And why isn't the field labeled as "Weight" not the right value?