I am not sure if this is possible not to present the thousand separator.
However, if you are using an 11.1.2.x version you can use the rule GetCellText in order to use the CellText value in the rule...
I cannot enter cell text, I have a rule that reads this value
Since version 126.96.36.199 you are able to read and write cell text from rules, the commands are:
HS.GetCellTextWithLabel("POVExpression", "CellTextLabel") and HS.SetCellTextWithLabel("POVExpression", "CellTextLabel", "CellTextString")