The best way to debug this is set a break point, and then see what the variable values are as you step through the code. You see the values by either hovering over the value or opening up the Locals (or Auto) window from the Debug / Windows menu. This should help you debug your code.

Do not use "+" to connect strings. Use "&". This is likely not your problem, but it is good programming practice (you do not add text, you add numbers).