switch to another TAB by code

Hello Helpers

I have a visual force page with 2 tabs

On tab 1 I have some components like grids and customr button

I would like to switch automatically from Tab 1 to Tab 2 when I press the custom button BUT ONLY AFTER the apex controller method associated to custom buton Action has completed

I tried to use oncomplete to achieve this. My problem is that the tab is switched but it looks like the operation in DoSonethingatApexside is not performed

<apex:pageBlockButtons >
<apex:commandButton action="{!DoSonethingatApexside}" value="Preview"
oncomplete="RichFaces.switchTab('{!$Component.theTabPanel}','{!$Component.tabPreview}','Preview')">
</apex:commandButton>
</apex:pageBlockButtons>

If I remove the oncomplete and press the custom button and switch tomTab 2 manually all Are OK
I see in tab 2 the results of the custom button action

any suggestions?

Thanks in adsvance
csbaa