You can do virtually anything you want to do in JMP, so yes, there are ways to do what you want. However, the structure you have is a data table, and it's defaults are based upon a column based analysis table structure, not a cell based structure like Excel.
To do what you are asking, I would do the following.
Go to "Column Info" for the percentage column.
In the Column Info window, remove the formula property. This will keep the values, but take away the formula.
Then change the "Data Type" from numeric to character