I have a different notion of the error: because there is nothing on the left side for it to be equal to; i.e.
something = dlookup("ChecksCompleted","dbo_tblCurrentStrategy" , "EngineerName = '" & me.cboOpCompleting.Value & "'")
The colon should not be there, but if it is, it does not generate a compile error for me but it does raise a syntax error at run time. However not passing the return value of the DLookup function to something does generate a compile error.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.