Prevent duplicates

Hi,

I'm quite new to microsoft excel.
First of all I will tell you what I am using excel for and what I need.

What I do: I have a company and I am listing all of my clients in excel. I ask them for their name, birth date, IP, email adress .....

What I need: Well I don't want to have double accounts which means I don't want members to register again with the same email and/or the same IP. I don't want to check that manually each time I get a new client. Isn't there an option or excel addon software for such things?

I want excel to give me some sort of sign if I write the same name/ip/email adress again.

I hope you understand what i want.
Thank you in advance

Try data validation

http://www.contextures.com/xlDataVal01.html

Use a formula from this site


http://www.mvps.org/dmcritchie/excel/validation.htm

Prevent Duplicate Entries, Q313185 -- XL2000: How to Use Data Validation to Prevent Duplicate Entries
=ISERROR(MATCH(A1,A2:A50,0)) in formula, and
=ISERROR(MATCH(A2,INDIRECT("$A$1:$A$"&ROW()-1),0)) in settings
Haven't really looked at this but it requires two parts to do what David Hagar accomplishes with a single formula. Chip's solution/example is for a fixed range and as such is not applicable to more generic usage.

HTH

VBA Noob

You can use Validation found in the Data menu to pop up a warning.

select the column or consecutive columns to apply the validation to and go to Data|Validation.

select Custom from the Allow dropdown menu.

enter formula: =COUNTIF(C$1:C1,C1)=1 where C1 is the top left most cell in your selection. Note the $ sign.

You can click the error alert tab to enter a message to display.

thank you guy.
It works. I used the second way

You really helped me a lot with this

Ok It's me again. I am back after using the second code for a year

I noticed that when I am copy pasting IP addresses this trick doesn't work. If I write the addresses manually it alerts me that it is already entered.

How can I get it work even if I copy paste text?