Hi Wayne,
First of all, I hope that the version of IC you indicated was a typo: 6.1A is very old and unsupported by Crystal Reports for Adagio. We install tables for versions 6.1B and 6.5A of Accpac Plus IC, and also tables for Adagio Inventory.
I probably will need more information as to why the selection criteria is not working. The 'syntax' appears correct; are you getting a formula error message or are the report results different than you expected?
The question I have is what you mean by 'subtotalling' the sales history amounts. Are you creating a report on the Transaction History file, selecting all shipments in the last 6 months, and subtotalling the amount field by Item number? Or are you creating a formula to add together the 6 Sales History fields from the Item Master file to determine your 6 months of sales?
This is important because you may not be able to use a formula (@Calc min} based on a subtotalled field in the "record selection formula". If this is the case, you should have this in the "group selection formula" instead. If your {@Calc min} formula is in the report Detail section, then this should work; it does for me.