How to calculate % in summary sheet from cell A9 in multiple sheet
 

Dear experts,
I have data on patients in excel file, with each patient's data placed on a
separate sheet. For instance: PatientA has data on worksheet "PatientA"
(Sheet2) where cell A9 is hemoglobin value.. PatientZ has data on worksheet
"PatientZ" (Sheet50) where cell A9 is hemoglobin value. I have a summary
worksheet called "Summary" (Sheet1). I need cell A9 in the "Summary" (Sheet1)
sheet to give me the percentage of patients whose Hemoglobin value is between
10 and 12 (that is percentage of A9 values in Sheet1 to Sheet50 with value
between 10 and 12). Any help is appreciated. Thanks.