The cell with the code just says "#REF!"
Its probably a sintax error..
What i want is: If the cell D3 is equal to "+" then the value of the cell I3 must be equal to "test1"
What you are asking for is impossible using formulas.
A formula can only alter the cell it is written in, it cannot alter any other cell.
Use of vba would be required to make this type of change.
It's syntax. Remove the () in the True, False components and use commas, not semicolons. Type this formula in Cell I3.