dbnull in a combobox

I'm using the code below to fill in a combox. The field can be NULL and I get an error msg when it is. I'm using the code below, but am having a problem on the line where I'm adding string.empty
(cmbAccount.Items.Add = String.Empty)...do I have this coded right?

VB Code:

Do While objDR.Read = True
                    If (objDR("vendor_name")) Is DBNull.Value Then
                        cmbAccount.Items.Add = String.Empty
                    Else
                        Me.cmbAccount.Items.Add(RTrim(objDR("vendor_name")))
                    End If

What's the error ? I suppose it's in the Add part of the cmbAccount object .

Try this code :

VB Code:

Do While objDR.Read = True
                    If (objDR("vendor_name")) Is DBNull.Value Then
                        cmbAccount.Items.Add[B](String.Empty)[/B]  
                    Else
                        Me.cmbAccount.Items.Add(RTrim(objDR("vendor_name")))
                    End If

thanks Pirate