=EOMONTH(TODAY(),-1)+1

=EOMONTH(TODAY(),0)

=NETWORKDAYS(A2,B2,D2:D10)

=IF(C2<A2,0,NETWORKDAYS(A2,MIN(C2,B2),D2:D10))

=IF(F2=0,"対象営業日なし",G2/F2)
