Unfortunately, the variable UHRSWORK1 is unavailable in the Online Analysis Tool. To see which variables are available, you will want to look at the variable selection in the interface (left hand side). You can use the expand option to see each variable by category. A similar variable, AHRSWORKT, is available. If you apply the following when creating a SDA frequency, you should not receive an error:
row: ahrsworkt
filter: ahrsworkt(35-*)
To have a bit more flexibility with your analysis, you may want to consider creating an extract through IPUMS CPS. You can see some more information about doing so in my response here.