Modules & VBA :: Inserting Field Value When Adding Record Using Data Entry Form?

I have a form for entry and some fields are computed or result of a query from another table. I have a function that looks up a value from another table like so

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Public Function GetTargetType() As Variant
GetTargetType = DLookup("type", "tblFormulations", "[tblFormulations!formulation]=Forms![frmNmsConsumptionEntry]![formulation]")
End Function
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Which works fine when I test in the immediate window.Then I have this form event. This however does not insert this value when I am adding records using my continuous form.

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Private Sub Form_BeforeInsert(Cancel As Integer)
Me!target_group = GetTargetType()
'Forms!frmNmsConsumptionEntry!target_group = GetTargetType()
'[tblNmsConsumption.target_group] = GetTargetType()
End Sub
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making sure I can insert this value once retrieved.