How to make headers in a DataGridView drop downs, and populate the column based on the value

I am new to VB, and am struggling to figure out how to make this work. I have 3 databases being used on the back end that are populated by forms. I want to create the ability for the users to generate custom reports and export them to a .csv file.

I have two problems (kinda) I am struggling to resolve..

I am using a datagridview, and can get the cells to populate the value from a combobox outside of the table (code below), but I would prefer the headers of the DGV to be the combobox. Does anyone know how to do this?

There are also roughly 20 values I want to provide options for in the combobox, and I can't find a way to better add these values than to manually enter each of them for all 20 rows (would make for a VERY long public sub) LOL. the below code works, but it won't scale. What can I use other than an IF statement so that the value selected in cmbColumn1 determines how the column is populated from the database?

Public Sub btnViewReport_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnViewReport.Click
    Dim OleDBC As New OleDbCommand
    Dim OleDBDR As OleDbDataReader
    Dim c As Integer
    c = 0
    If cmbColumn1.Text = "Patient ID" Then

        With OleDBC
            .Connection = conn
            .CommandText = "SELECT * FROM tblPatientsRecord WHERE PatientID like '%" & txtSearch.Text & "%'"
        End With
        OleDBDR = OleDBC.ExecuteReader
        DataGridViewReport.Rows.Clear()
        If OleDBDR.HasRows Then
            While OleDBDR.Read
                DataGridViewReport.Rows.Add()
                DataGridViewReport.Item(0, c).Value = OleDBDR.Item(0)

                c = c + 1
            End While
        Else
        End If
    End If
End Sub