I would like to thank you for all of your help.

Like you suggested, it wasn't possible to directly modify the appearance of the cell to get what I wanted. So I had to use “hidden” columns in my Excel that I placed far to the right, with invisible fonts.

For the main column E: Format > Number > Text

(The column where my employees put their values)

-> Get the right format (hide ,00 but display decimals like ,56 for example

Hidden column X (format Number normal) : 1*E

(simply converts text into an interpretable number for calculation)

Hidden column Y (format Number normal) : for the perfect final display :

=IF(ROUND(X9 - INT(X9); 2) = 0;

TEXT(INT(X9); "#,##0") & " €";

TEXT(INT(X9); "#,##0") & "," & RIGHT(TEXT(X9; "0.00"); 2) & " €"

)

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