With this current formula:
=IF(O2<21,"",IF(AND(O2<28,M2TODAY(),Q2100000),"X ",""))


What would i add to the formula if i wanted to also indicate that if there
was no date in M then i want to consider it meeting the condition along with
the other to. ie if m2 today or blank, and q2100000 and 02 is between
21-28 days?