Which text field onFocus called the function?

[Al Smith]

Hi,
Question:
Is there something that can be passed to a Javascript function that tells the function which element index called it?

I'm doing some date/time verification with Javascript.
DateTime2 must be after DateTime1 and DateTime3 must be after DateTime2. DateTime1 comes from a database.
A onFocus in DateTime3 calls the function to verify that DateTime2 date is after DateTime1. Likewise an onFocus in the field after DateTime3 verifies DateTime2 and DateTime3.

strHtml=strHtml & "function check_isDate(day,month,year,x,what)"
strHtml=strHtml & "{"
strHtml=strHtml & "   if (!isDate(day,month,year))"
strHtml=strHtml & "   {"
strHtml=strHtml & "     alert(""Invalid "" + what);"
strHtml=strHtml & "     document.CallInfo.elements[x-3].focus();"
strHtml=strHtml & "   }"
strHtml=strHtml & "}"

Right now I'm hardcoding an element number (x in the above) in the function call.The purpose for this is so I can set the focus back to the field that contained the error.

I hope this makes sense.

Al.