I think you can use custom fee field feature to solve this issue. Basically, you can create a dropdown custom fee field to allow users to choose number of days they want to attend and charge them based on the number they select. Please see
documentation.joomdonation.com/2-events-...st-custom-field-type
for instructions
With that in mind, I think you can setup it as below:
1. Create a new custom field, type Number of days for example
2. Set Fee Field to Yes
3. In the values, enter :
1
2
3
4
5
4. In the Fee Values, enter
5
10
15
20
20
After that, please try to register for that event and choose the number of days you want, the fee will be calculated based on the value you select
Regards,
Tuan