We all know that data validation is a very useful feature in Excel. You can use data validation to create a drop-down list in a cell and limit the values user can enter. But, do you know that you can use data validation in a multitude of ways to prevent users from entering wrong data?
Here is a practical application: Prevent users from entering duplicate values in a range of cells.
For eg. you are making an invoice. Wouldn’t it be cool if Excel prompted you when you enter a duplicate line item so that increase the item quantity instead of repeating it.
Here is a 3 step tutorial to do just that.
Step 1: Identify the range of cells where you want only unique values to be entered
This is simple. All you have to do is find the range where you want to control the user input. Lets say the range is B4:B11
Step 2: Set up Data Validation to prevent duplicate entries
Select the range (B4:B11) and go to data validation (Excel 2007: Data Ribbon > Data Validation, or press ALT+AVV)
Now, specify the validation type as “Custom”, this will allow us to use formulas to check for valid data. In our case, we need check if a particular entry is duplicated in the range B4:B11. This can be easily done using COUNTIF formula [learn COUNTIF Formula in plain English].
Go to the formula field and type the countif formula like this: =COUNTIF($B$4:$B$11,B4)<=1
Also, you can set up the “Error Alert” so that you can show a custom message when a duplicate value is typed, like “You have already added that product” message.

Once you set up error message, it will show up like this:

Step 3: Sit back and Relax
The third step is all too familiar. Now that you have prevented duplicate entries in your spreadsheets you can sit back and relax. May be read a few more spreadcheats.
More kickass stuff on data validation (and working with duplicates) using excel
There are a ton of useful articles on the site related to data validation and working with duplicates using excel. Here is a sample. Get started and learn something useful today.
- Data Validation Tricks in Excel [with downloadable tutorial]
- Remove Duplicate Values from a Range in Excel
- Using Array formulas to find if a list has duplicates
- Working with duplicate items in Excel [several examples]
- Examples & Articles on Excel Data Validation
This post is part of our spreadcheats series (yes, the series is still going after one year 😛 )

















6 Responses to “A quick personal update”
Thank you for the personal update. It was quite encouraging and a breath of fresh air in my Inbox. Take care and stay safe.
David
Doctors advise:
Virus obstructs lungs with thick mucus that solidifies.
Consume lot hot liquids like tea, soup, and sip of hot liquid every 20 min
Gargle w antiseptic of lemon, vinegar, & hot water daily
It attaches to hair/clothes detergent kills it, when come from st go straight shower
Hang dirty clothes in sunlight/cold overnight or wash immediately.
Wash metal surfaces as it can live on them 9 days
Do not touch hand rails
Do not smoke
Wash hands foaming 20 sec every 20 min
Eat fruit/veg and up zinc levels.
Animals do not spread it
Avoid common flu
Avoid eat/drink cold things
If feel sore throat do above immediate as virus is there 3-4 days before descends into lungs
Would love help with my database mgt in excel.
Thanks for being thoughtful of us.
BTW How do you track your expenses/income in excel? Can you share the worksheet please.
Stay safe you and your family, best wishes.
Thanks for the update and happy to know that you and family are doing good. A 21 day lockdown has now been announced in India (I live around Kolkata) so it's uncertain times ahead. I check up on your wonderful articles often and will do so even more regularly now. Stay safe and God bless.
Hi from Argentina, I follow you for a lot of years now. We here are in a quarantine for 2 or 3 weeks, because the pandemia.
Excel is also my passion and I came here looking for a Num2Words formula, but in spanish. If anyone have it, please let me know.
Best regards.
Pablo Molina
La Rioja - Argentina
I'm glad to have your personal update. I'm from India & following you for so many years. Cheers to have any further personal update.