I am trying to limit the number of decimal places to one decimal place for a particular data field. (###.#) "without rounding"

The data being pulled from my database is numerical data and it is in the format of 2 decimal places (###.##).


The first function I tried was ToNumber and then I would adjust the number display by using the "Format Editor-Number Tab":
(ToNumber({tests.test_res_val})

The problem is, when I go to preview my report, I am getting an error message stating that "The string is non-numeric.".



The other function I tried was Truncate:
Truncate({tests.test_res_val}, 1)

The problem with this is that it still sees {tests.test_res_val} as non-numerical with the error reading "A number, or currency is required here.".