Your ReportViewer2.LocalReport has a method called SetParameters. Create a new List(Of ReportParameter), add your textbox contents with the name of the parameter in your report and send it in
Public Overrides Sub SetParameters(ByVal parameters As System.Collections.Generic.IEnumerable(Of Microsoft.Reporting.WinForms.ReportParameter))
Member of Microsoft.Reporting.WinForms.LocalReport
Summary:
Sets report parameter properties for the local report.
Parameters:
parameters: An array of Microsoft.Reporting.WinForms.ReportParameter objects that contains a list of the report parameter properties.