Is it possible to make a certain field NOT accept certain things?

I am wondering if it is possible to make it so that certain fields in one of my forms can be set to not accept an answer with a special character in it. Also, can I cap the answer by a certain number of characters all together?

I am using API integrations and when the data transfers to Quickbooks, if the client has a special character in the form it stops the entire process. The same thing happens if their response is too long.

Please advise.

Please check this demo form: https://form.jotform.com/80948734055969

Is that what you're trying to achieve? If you put "a" or "c" the Submit button will disappear. If yes, you can use the Show/Hide conditions and if the field contains a specific letter or character the Submit button will be hidden.

Here's the result:

If you want to check the condition settings of the demo form, you can clone it by following this guide: https://www.jotform.com/help/42-How-to-Clone-an-Existing-Form-from-a-URL