It is entirely possible to do this:

Create a hidden field in the details record to hold the value you want to see in the header

Name the textbox "header_field_1"

populate it with the database value you want to display on the header.

Next, within the header, reference the report textbox in an expression where you store the value: =ReportItems!header_field_1.value

note that this is different from referenceing the data value from your dataset.

HERE IS THE ISSUE THAT I CANNOT FIGURE OUT THOUGH.....

When the report renders it looks fine... but when you go to print it, the headers become static and only the data from the first row is printed.

If anyone figures this one out then you have my votes.