You keep posting questions about the exact same WHERE clause with exactly the same apparent error in each one. SO users dutifully point out your error and then a few days later, you show up with a related question utilizing the same faulty WHERE clause.
DLookup Problem:
txtContSunStart1.Value = DLookup("Start1", "tblContract", _
"TestId = " & _
lstResults.Value & _
"" And "Day = 'Sunday'")
VBA Update Query:
DoCmd.RunSQL (" Update tbltesting set IsDiff ='Yes' where empid= " & Me.txtEmpId.Value & " and testid= " & Me.txtAutoNumber.Value & ";")
VBA SQL Problem
DoCmd.RunSQL ("insert into tbltesting (IsDiff)values ('Yes') where empid= '" & Me.txtEmpId.Value & "' and testid= '" & Me.txtAutoNumber.Value & "'")
And then in the current question:
lstDiff.RowSource = "select TestScenario,TestId from tblTesting where empid= '" & Me.txtEmpId.Value & "' and testid= '" & Me.txtAutoNumber.Value & "'"
You are having difficulties with exactly the same set of problems repeatedly.
Here are the rules for concatenating SQL strings with the correct delimiters in Access:
numeric values do not need delimiters:
"... AND testid= " & Me!txtAutoNumber
text values need quote delimiters. In Access, it's general practice to use double quotes, but much easier to use single quotes since it's a pain to type double quotes in a form that will work (typing """ or """" depending on context is counterintuitive and silly to me, so I always define a global constant that holds the double quote symbol and concatenate with that).
"... AND textfield=" & Chr(34) & Me!MyTextField & Chr(34)
date values use the # delimiter:
"... AND datefield=#" & Me!MyDateField & "#"
Boolean fields require no quotes and it works best to use True and False:
"... AND IsDiff=True"
These rules apply both to WHERE clause criteria and to SET statements in UPDATE queries. The rules apply in writing a SQL string that you pass to DoCmd.RunSQL or CurrentDB.Execute, as well as to writing SQL strings to be used as the recordsource of a form or report or as the rowsource of a combo box or listbox.