Simulate click on button

I am testing an application that have the following html code:

...
<input 
    type="button"
    class="picto modif"
    onclick="hideDiv('divGlobalResult');showDiv('divForm')"
/>

When the user clicks on this button, the div divGlobalResult is hidden and the div divForm is shown.

I want to simulate this action with Selenium. Here is how I did:

focus      css=input.picto.modif
fireEvent  css=input.picto.modif  click

However, the divForm appears while the second div divGlobalResult stays on the screen...

What am I missing?

---

function hideDiv(idDivElement) {
    $("#" + idDivElement).css("display", "none");
}

function showDiv(idDivElement) {
    $("#" + idDivElement).css("display", "");
}