how to send a value from a form to a reprt in access 2013

hi

i have a veriable in a form that contain some sql string and i want to send this value to a report recordsorce and then open this report based on this sql source

i wrote this code in the report

Public Sub ControlReport(a As String)
If Not IsNull(a) And Not a <> "" Then
    Me.RecordSource = a
    Me.Requery
End If
End Sub

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and in the form i have this code

DoCmd.OpenReport "ListProductrsReport", acViewPreview
reports!ListProductrsReport!ontrolReport (sqlString)

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but i don't can to compile the code on the form, what is the problem with my code?

thanks a lot