I have four variables: ID (col HZ), Pick (col IA), Type of Visit (col
IB), and Current_Day (IC). ID is unique code and is repeated for every
visit; Pick takes only the last visit and codes it as 1, else 0; Type
of Visit picks its values from another variable that ranks the visit as
1, 2, 3...i and outputs either "N" or "R"; Curr_Day checks the value of
the date of visit to between 21st of previous month and 20th of current
month (e.g. March 21 to April 20, inclusive) and ouputs 0 or 1. Thus if
I want to pick all visits during the reporting period I simply
autofilter and select Curr_Day=1. I can further select single clients
from "Pick". However, a client can make more than one visit a month. In
my formula, only the first visit will be picked as new, the rest are
revisits.

HZ IA IB IC
3 1 N 0
8 1 N 1
17 0 N 0
17 0 R 0
17 1 R 1
18 0 N 1
18 1 R 1

formulae used
IA "=IF($HZ2-$HZ3=0,0,1)"
IB "=IF($EG2=1,"N",IF($EG2<1,"R",""))" where EG9 rank of visit (not
among the 4 fields)
IC "=IF(AND($DJ8$IR$2,$DJ8<$IR$3),1,0)" where DJ is date of visit and
IR2 start date, IR3 is end date

How can I create a formula that codes all visits as new so long as the
first visit falls within the month of interest? Will this solve my
problem, since at the end of day, I just want to analyse new visits and
revisits and pick clients only once, regardless of the number of visits
within the month. I would really appreciate any assistance on this. I
have reached my limit of creativity.
Cheers.