Add GridViewComboBoxColumn to exisiting column

[Won]

Please, remove this post. I moved it to Gridview forum. This was wrong place. Sorry!

Hi! 
I am trying to implement GridViewComboBoxColumn on gridview for existing"DEPARTMENT_ID"
colum.
I tried below and it works fine, but it is adding another column on the gridview instead of replacing existing "DEPARTMENT_ID" column.
1. What should I change?
2. What property will remove a scroll bar on GridViewComboBoxColumn?

 
 With Me.rgvEmployee

            .Columns("EMP_ID").HeaderText = "EMP ID"

            Dim deptComboboxColumn As GridViewComboBoxColumn = New GridViewComboBoxColumn

            With deptComboboxColumn

                .UniqueName = "DeptColumn"

                .HeaderText = "Dept"

                .DataSource = From q In db.MST_DEPARTMENT _

                              Select q.DEPARTMENT_ID, q.DEPARTMENT_NM

                .ValueMember = "DEPARTMENT_ID"

                .DisplayMember = "DEPARTMENT_NM"

                .FieldName = "DEPARTMENT_ID"

                .Width = 200

            End With

            Me.rgvEmployee.Columns.Add(deptComboboxColumn)

        End With