Left Expression is of type string in lookup

Left Expression is of type string in lookup

After reading a number of posts, I understand the issue that my lookup is returning an integer and my initial data is a string. I've tried following the advice in the one of the forums and creating a variable to convert my lookup iD to the correct field. But I get an error message now on the variable.

If the two elements were strings my code would look like:
 Email == input.Employee   


meaning that the field from form Ticket_Entry would perform a look on the field employee in form Employee.

Of course it returns the ID from that data. I've tried the option to convert to the correct form the ID to the actual email address with:

stringfixed = Ticket_Entry[ID == input.employee];

But its incorrect. Doesn't like the string.

Any help is appreciated.