Sales Quotation Error : Item - Form item is not editable

Hi all,

i want to create a Sales Quotation tru Sales Quotation form. what i did is i open the form and put the values inside the fields in the form. this is my code:

Dim oMenu As SAPbouiCOM.MenuItem = SBO_Application.Menus.Item("2049")
                        Dim oFormQ As SAPbouiCOM.Form
                        Dim oFormsId As String
                        Dim oEdit As SAPbouiCOM.EditText
                        Dim oItem As SAPbouiCOM.Item
                        Dim oCell As SAPbouiCOM.Cells

                        oMenu.Activate() ' Click menu Sales Quotation

                        oFormsId = SBO_Application.Forms.ActiveForm.UniqueID

                        oFormQ = SBO_Application.Forms.Item(oFormsId)
                        oFormQ.Left = 300 ' hide the form

                        ' BP Code Edittext
                        oEdit = oFormQ.Items.Item("4").Specific
                        oEdit.Value = "CNAR-0038"

                        ' Remark Edittext
                        oEdit = oFormQ.Items.Item("16").Specific
                        oEdit.Value = "Remark"

                        ' Matrix Item/Service
                        oMatrix = oFormQ.Items.Item("39").Specific

                        ' Description Column
                        oEdit = oMatrix.Columns.Item(1).Cells.Item(1).Specific
                        oEdit.Value = "SERVICE NAME"

                        ' Amount Column
                        oEdit = oMatrix.Columns.Item(12).Cells.Item(1).Specific
                        oEdit.Value = "1000"

the problem is i got error "Item - Form item is not editable" when putting value in Amount column. the column in the form is visible and active.

how can i solve this? please help.

thanks in advance,

azif.