[dba-Tech] Report problems

The table of interest contains a column called Marked, and various controls
to mark rows for inclusion (i.e. age = 12, mark all, then status =
'Inquiry', mark all, then Find Marked which shows the sum of both sets. Then
a button invokes a report preview, and its code says:

        DoCmd.OpenReport ReportName:="RiderList_rpt", View:=acPreview,
WhereCondition:="[Marked]= " & True

And I get an input box asking me for a value for Marked. If I type in True
or -1 the report works. If I type in nothing it displays zero rows.

I have tried several variants of this command, such as:

        DoCmd.OpenReport ReportName:="RiderList_rpt", View:=acPreview,
WhereCondition:="Marked = " & True
        DoCmd.OpenReport ReportName:="RiderList_rpt", View:=acPreview,
WhereCondition:="[Riders].[Marked] = " & True
        DoCmd.OpenReport ReportName:="RiderList_rpt", View:=acPreview,
WhereCondition:="[Riders].[Marked] = True"

And so on. Nothing seems to prevent invocation of the inputbox asking for a
parameter value for Marked. I don't understand what I'm doing wrong.

The report in question simply looks for Marked = True. It's not based on a
query or anything. It just looks at the one table. The filter "Marked =
True" is passed in as indicated above, but it doesn't seem to work.

Any suggestions?

TIA,
Arthur