Javascript error

Thank you for you response.
T
his is the function that the error refers to: Which is part of the WA_eCart_Definition_VB.asp.

"function WA_eCart_DisplayInfo(cartObj, ItemProperty)
retVal = ""
if (NOT WA_eCart_IsEmpty(cartObj) AND NOT WA_eCart_EOF(cartObj)) then
retVal = (eval("cartObj.Items(cartObj.DisplayIndex)." & ItemProperty))
end if
WA_eCart_DisplayInfo = retVal
end function"

Line 81 is "retVal = (eval("cartObj.Items(cartObj.DisplayIndex)." & ItemProperty))"

I've looked and I can't see a problem with this code. This happens when I click the Add To Cart Button. What is good is that the item is added to the shopping cart, but this error is stopping the shopping cart from coming up.