Adding new sheet to existing userform

Hello!

Nickmax1 helped me out last week with some coding so my users had to choose between 2 combo boxes to go to the desired worksheet. I've attached the Test workbook he created. I had no problems adding "Construction MD" and Construction Repair", but I can't add "Exempt". I get a "run-time error 9" and "subcript out of range". If I click "Debug", it takes me to VBA and highlights
ThisWorkbook.Worksheets(strWS).Visible = True

I added my workbook with the hopes that you can figure out what I've done as I'm assuming it's something horribly wrong!! Any suggestions??

Thanks!!!!