events triggered when a data input control such as text box or drop down list receives focus

I need to display a help message for each of the data input controls (text box drop down list for example) in a web form when the control receives focus, the message will be displayed at a message box. I can't find an event handler for that for text box, is there a way to achieve this?

By the way, we take aside the use of tooltip at this moment

 

 
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