Error Null Type Conversion

[jclover]

I'm using Microsoft Access to try to put together a form that enters data into a table when the form is closed, not a typical live form. Several fields are combo lists that pull from various queries. When I execute the code, I keep getting this error:

1 field(s) set to Null due to type conversion.

Here's the code:

Dim strSQL As String
Dim Eff_Date As Long
Eff_Date = Me.Eff_Date

strSQL = "INSERT INTO tblMPR_Price([MPR_ID],[SKU],[Discount],[Eff_Date]," & _
"[DeadOld],[DeadNew],[MAPOld],[MAPNew],[InvOld],[InvNew],[Rate]) " & _
"VALUES ('" & Me.[MPR_ID] & "','" & Me.[SKU] & "','" & Me.[Discount] & "'," & Eff_Date & _
",'" & Me.[DeadOld] & "','" & Me.[DeadNew] & "','" & Me.[MAPOld] & _
"','" & Me.[MAPNew] & "','" & Me.[InvOld] & "','" & Me.[InvNew] & _
"','" & Me.[Rate] & "');"

DoCmd.RunSQL strSQL

Here's the field types.

Dead*, MAP* and Inv* fields are currency
Rate is Number
Eff_Date is Date
MPR_ID is Number
SKU and DISCOUNT are Text

I've noticed it seems to be linked to if the "DeadOLD" and "MapOLD" fields have a null value (since the value is populated by a query, if there's no match in the product type, no OLD pricing is pulled). Any ideas on how to handle this? The data gets tansferred still, it's just a nuissance.

[Rabbit]

'Single Quotes Mean Text'
#Hash Signs Mean Date#
And no surrounding characters means it's a variable or a number.