I found that a problem too...( Hey Access, its not really complex)
BUT what I did is:
create a text box (mine is invisible to user) called txtRng. When the user clicks the open report button, a small code writes the 'text' version of the date range ....
txtRng = "From " & [Forms]![Purchase Report]![From] & " to " & [Forms]![Purchase Report]![To]
then opens the report, and the query has a virtual field : [Forms]![Purchase Report]![txtRng]
Access cant calculate that formula but it CAN just display the text box value.