This is yet another of your myriad questions that could be answered by spending a few minutes reviewing the Access help files or Googling for a bit. I really wish you would stop posting these on StackOverflow. I don't see that they serve any purpose but to allow people to up their reputation, which is the worst possible motivation for posting on SO, in my opinion. And 75% of your questions aren't even programming questions -- they are more appropriate to SuperUser.com, in my opinion.
Please stop.
In any event, I'll answer your question:
You should use [Forms]![Enter Data]![comboCup].
As @Remou has said, the .Text property of an Access control is available only when the control has the focus.
The .Value property is redundant, as it's the default property of all Access controls, so these two are equivalent:
[Forms]![Enter Data]![comboCup]
[Forms]![Enter Data]![comboCup].Value
(note also that properties like .Text and .Value are separated by the dot operator and not the bang, which delineates collections)
One issue that can be of concern is if you want to use the value of the combo box in the SELECT statement of an APPEND query. In that case, you would be advised to declare the combo box as a parameter in your saved query. If you do not, it can cause the row to not be inserted, whereas if you declare the parameter, it will resolve to the Null that is the value in the referenced combo box.