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Your LimeSurvey version: url=https://www.limesurvey.org]LimeSurvey Cloud[/url] [url=https://jasperdh.limesurvey.net/dashboard/view#modalSystemInformation] Version 6.15.22[/url
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Hello, I'm building a survey that is to be filled out daily by the participants over a period of three weeks. I'd like the participants to be able to start on the day that works for them, and possibly also, to take some extra time to do the study (e.g. to give 21 responses, but over 4 weeks). The key difficulty is that there are some extra questions, which should only show up on certain days. I found an easy solution to this, by tying these questions to specific dates, but then the participants lose all flexibility to do the study according to their own schedule. Is there a way to do this in LimeSurvey? Preferably, so that participants see the extra questions on what for them is the 7th time that they open the study? Or otherwise, so that they see it on the 7th day from when they started the study? 
Each response should count as a separate response and not continue from the previous response. I wasn't able therefore to solve this with a hidden day counter variable. 
Any help would be very much appreciated!

You can use the function "statCountif()" to check, how many times the respondent completed the survey already. 
[url] www.limesurvey.org/manual/StatFunctions [/url]
These functions are included in LimeSurvey. Maybe you have to do a "scan file" in the plugin management andinstall or activate.

I assume that it is a closed survey. So you can use an additional attribute as criteria.
This way you can force your "special" questions to appear on the seventh time, or so.

Joffm