There are: 3 fields for user input, one of which is for output. If the user entered values in the fields, then the third automatically counted the sum.
Now I add the drop-down lists to the 1st and 2nd fields, and the new one is the final field for the third drop-down list. The 3rd drop-down list with a new field should consider the amount of the category selected in it.
How to implement?
