Lookup table as a validation condition

Dear All ,

I was trying to check if its possible to attach a .csv file with my form in order to validate the value entered by the user to check if the entered value exists in the .csv file. In XLS forms , we use the pull data function inside the constraint field which will check if the entered value by the user exists in the .csv file. I have done some research on this and understood that this could be done using “Lookup tables” but there wasn’t a clear explanation on this. as an example. I want the user to enter a pin number which has 4 digits but I want the form to check if this pin number exists in the .csv file that I have.

Thanks in advance.