hi Vikki, there's no trickiness, feel free to go in there and play around (in the sandbox, if you are not certain). Calculated fields are very much like excel calculations, so if you even have an excel wizard on staff, they could probably help you with the syntax from time to time. It can be done in a few different ways but for what you specifically ask for, the workfront support site "https://support.workfront.com/hc/en-us/articles/217196767-Understanding-Calculated-Data-Expressions" title="https://support.workfront.com/hc/en-us/articles/217196767-Understanding-Calculated-Data-Expressions">
https://support.workfront.com/hc/en-us/articles/217196767-Understanding-Calculated-Data-Expressions and the calculated field itself will both help you. From the support site page, you can pick out the calculation you want (it's the first one listed). From your calculated field, you can select the expression from the first selection list (Expressions), and whatever you want from the second selection list (Fields). For your specific example, you would double click on the adddays expression on the first list, position your cursor before the comma, then select your field from the second list. Your number would go after the comma. The resulting calculated field would look something like: ADDDAYS(YOURFIELDNAME,-30). The only other caveat folks would add is that sometimes it would be helpful to surround your fieldname with curly braces, like this: ADDDAYS({YOURFIELDNAME},-30) Remember to choose a calculated field "format" as well. A lot of times, I forget and skip over this in my excitement over getting to the calculation part, and then I realize I left it as "text" when really I had meant to do something date related with the result of the calculation. In terms of logic, I am not sure what you want to add. Maybe something about how if the field isn't blank [you can definitely get around this by just making it a required field as well]? So in that case, you would add on to your current calculation by saying IF(!ISBLANK({YOURFIELDNAME}), ADDDAYS({YOURFIELDNAME},-30)) --if it's not blank, subtract 30 from your custom field, otherwise it just stays blank. If you're specifically referring to display or skip logic, I encourage you to read up on display logic or skip logic in the support site so you can redirect your questions (display or skip logic refers to visibility that relies on a series of choices from radio buttons, checkboxes or dropdowns). -skye