Can an employer force an employee to do this

[JLAVG]

What is the name of your state? Indiana

I know that Indiana is an "at will" state.
That being said, can an employer force an employee to use a talent that he wasn't hired for?
For instance, if someone was hired as a construction worker, but the owner discovered said employee was a mechanic, that worked on vehicles as a side hustle. Could the owner force said employee to replace the head gaskets on a company truck, or install a transmission, at his normal pay, to keep from having to pay what a shop would charge?
Or, if someone was hired as forklift driver in a warehouse, and the company found out said employee has a CDL. Could they force said employee to haul trailers from one location to another while paying said employee the warehouse forklift driver pay?
If an employee in this situation were to refuse, could they be fired for just cause?

 

[cbg]

Barring a legally enforceable contract or CBA that expressly limits what jobs the employee can be asked to do, the employer can ask the employee to do anything that is not illegal, unsafe by OSHA standards, or for which a license or certificate is required that the employee does not have. The employee can refuse; the employer can fire them if they do.