Tips & Tricks 5 – Allow Entry of Dates if they are not Weekends Posted on May 31, 2014October 29, 2014 by Vijay A. Verma 1. Select the Cell > Data Tab > Data Validation > Data Validation 2. Under Settings Tab, in Allow, select Custom 3. Put following formula =WEEKDAY(A1,16)>2 4. Customize your Input and Error Message as per your requirements.