How to increment the value of a Numeric Field box

I have a PDF form that has a Numeric Field box in it. I want to add a link that will increment the value in the Numeric Field box when clicked on. I got as far as making the link. Using the ACTIONS tab of the LINK PROPERTIES dialog box, I selected the action: RUN A JAVA SCRIPT. Now It wants me to type in the code. Not knowing much about Java, I have tried to guess at some likely code with no success (like NumericField.Value = NumericField.Value + 1). Why are you laughing? I usually get the error message Missing: before statement 1: at line 2. I would be grateful if someone would supply the correct code lines with the correct punctuation. Im guessing it will take 3 or 4 lines. Thank you, Fred

PS I have Adobe Acrobat 8 Professional and a PC with VISTA.