Data Validation in Excel -

• To use Data Validation in Excel, first select your table. 
• Go to the Data Tab, here you will see the option of Data Validation, click on it 

• Clicking on it will open the dialog box

• In this dialog box, you will see 3 tabs Settings, Input Message, Error Alert
• In the Settings tab, you have to set Data Validation Formula, with this you can create a drop-down list in any cell. 
•  The other two tabs Input Message and Error Alert let you tell the operator what to type in the cell. 
• If Data Validation is installed in the cell and if someone tries to type it wrong then it will not be able to do it.