Bearing in mind its based on my code, I'd better answer that....
There is no reason why tblUsers is needed before the Active field in the WHERE clause. It can be removed.
I also agree with creating a sql string so it can easily be debugged before execution
Using Dim strSQL As String would be better...otherwise its a variant
However, it isn't necessary to include the quotes around the function in the SET clause, though they are essential in the WHERE clause.
IIRC, using them in the SET clause will make the query less efficient i.e. slower, but I would need to test whether I have remembered that correctly.
The ( ) brackets can also be omitted