EXEC (select... ) problem Help!

How can I get this to work?
declare @WkEmpID
declare @sql varchar(1000)

set @sql = 'select distinct @WkEmpID = EmpID from Employee'
exec (@sql)

Now this is a simplified version of a more comples query which is forcing me
to use this method rather than a simple SQL query. The big problem is getting
the 'EmpID' value into the local variable of '@WkEmpID'. Please help!
.