still error sum

So Man!

THE ERROR STILL REMAIN! NOW..YOU CAN TRY WITH JUST A TEXT BOX

The moltiplication inside the textbox is right..but the sum into the form calculation is wrong

The sum is correct, you are summing  Totale TM1 in € + Totale TM2 in € + MITSUBISHI.

In the following example:

Totale TM1 in € = 210

Totale TM2 in € = 60

MITSUBISHI =  999(because I selected Mono Split 9000 which assigned value is 999)

Here is the result Result:

Let us know if you have more questions.