Can't find a range of values in a query

[cbc]

I have a database of patients and their weights, one weight for each of the 12 months. I want to set up a query where my rows are the patient names and the columns are their weight, one column for January, one colums for February, etc. I want to design the query so that it will result in those patients who have lost between 1% and 5% of their weight in the past month, that is, their current weight is between 99% and 95% of their last month's weight. The expression builder has been of little help

Thanks
cbc [sig][/sig]