Afterupdate cbo, Insert and text

It's always a good idea to create an extra SQL variable, but when you think the error comes from your UPDATE, then you need to look at your data. Cause your way of SQL string concatenation is vulnerable for SQL injection, thus it may fail due to single quotes in your data. Also as your ID seems to be numeric, enforcing this by using CLng() can help you to spot errors in data. And you need error handling with On [Local] Error GoTo LocalError (see attached file).

Dim Sql As String

Sql = "UPDATE tblProjects " & _
  "SET Buy_CP = '" & Replace(Me.cboBuy_CP.Column(1), "'", "''") & "' WHERE ID = " & CLng(Me.ID) & ";"
Debug.Print Sql
CurrentDb.Execute Sql

Select allOpen in new window

As ready to use-solution:

a) using a function for escaping quotes or NULL:

Dim Sql As String

Sql = "UPDATE tblProjects " & _
  "SET Buy_CP = " & SqlQuoteNull(Me.cboBuy_CP.Column(1)) & " WHERE ID = " & CLng(Me.ID) & ";"
Debug.Print Sql
CurrentDb.Execute Sql

Select allOpen in new window

b) with some error handling

Private Sub YourMethod()

  Const MSG_UPDATE_ERROR As String = "Error during update."
  Const SQL_UPDATE As String = "UPDATE tblProjects SET Buy_CP = {0} WHERE ID = {1};"

  If Not SqlExecuteFmt(SQL_UPDATE, SqlQuoteNull(Me.cboBuy_CP.Column(1)), CLng(Me.ID)) Then
    MsgBox MSG_UPDATE_ERROR, vbWarning
  End If

End Function

Select allOpen in new window

sql.vba

Thank you guys.... appreciate it much. I have not been able to get away to test  yet... shouod be able to tomorrow at latest. Enjoy the weekend!

my code was correct...my issue was something else.  Thank you...appreciate the advice and comments. 

In this case.. not really. Then there was "with some error handling" missing to catch the error where it really happened.