Data List Validation

Use the below procedure if you want to limit the data values enetered
in a column.

(User will select the value from a dropdown)

* List down the unique values to a different column.
* Select the complete column where the user will enter the values.
* Goto Data --> Data Validation
* In "Allow" dropdown, select "List"
* Click in the "Source" and select the range of the unique values.
* Click OK.