How can I hide the entry box in a Spreadsheet to Form Widget ?

I hope you are trying to disable the text box entry field in the Spreadsheet to form widget. You just want to have Calcul button visible and not the text box above. 

If that's the case, then copy the below CSS code in your Spreadsheet to form widget Custom CSS settings. 

.input-box {

    display: none;

}

This is how it looks after entering the code. 

Please injecting custom CSS to Widgets is different than injecting it to the form designer. Please refer to the article "How to inject CSS Codes to Widgets"

I hope this helps, let us know if you need further information.

Thank you AshtonP, it works perfectly!

Thanks again !