Using value from Dataset Column in a formula

I have been trying to use the date from another dataset in this schema and then generate a random date within a range of three months from that date in another field but I am getting an error:

error: Could not access blank value: Use || to provide a default value for blank fields. Example: (my_field || 0) + 1

Thanks

It looks like you need to parse the __DOS_To column as a date. This should work:

Date.strptime(field('__DOS_To'), '%m/%d/%Y')-days(random(0,90))

Thank you it worked fine.