calculation query

Hi fellow members,

I have a formula query?

I have created the following formula to give accurate readings for employee
holiday annd staff training register

=IF(COUNT(E4:E13)>2, "NOT OK","OK")

this formula allows me to see if it is 'ok' or 'not ok' to allow them to take annual leave
if less than 2 members are off in the department.

what i am now trying to achieve is now that i have used a numeric value to give me that answer i would like to change it to dominate a letter of the alphabet but still give a running total of number of days taken for holiday but not for sick days, public holidays or traning

please see the attached speadsheet

thank you dave