The conditional statement attempts to convert all variables to Double and then adds them up to compare against 38.30. However, the string "9.1" cannot be directly converted to a Double with CDbl because it is not in a correct format that can be recognized as a number (it might be due to the fact that it's a string with a comma instead of a period for a decimal point, depending on the culture settings of the system). This will cause a runtime error during the execution of the conditional statement.References:

Microsoft Visual Basic Guide: Type Conversion Functions