The "." key character from the NumPad is automatically replaced with a comma "," by Excel.
Unfortunately the TIWAdvEdit has no built-in functionality to replace this character and only accepts the character as defined by the DecimaplPoint property.
As a workaround you can try replacing the "." character with a comma manually by using the OnAsyncKeyUp event. Example:
Unfortunately the functionality to automatically replace the "." numpad character with a comma is currently not supported in the IWDBAdvEdit control. I'll investigate if this feature can be added in a future version.