javascript onselectstart Description
| onselectstart | NN n/a IE 4 DOM n/a |
| Bubbles: Yes; Cancelable: Yes | |
Fires immediately after the user begins dragging a selection on a body element or form control text. If the selection extends across multiple elements, only one event fires, and its target remains the element where the selection began. Canceling this event in the <body> tag (onselectstart="return false") can prevent undesirable and inadvertent user selection and scrolling interaction. |
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| Typical Targets | |
All rendered elements. |
|

Declare a variable say:
var enableOnSelectEvent = true;
On your <input>s add onmouseover and onmouseout events:
enableOnSelectEvent = true/false;
<body onselectstart="return !enableOnSelectEvent">
It should work.
Meanwhile, I've found that SPAN elements won't implement it, but DIV elements will, BUT only to turn off selecting the contents of a DIV. If a DIVs parent element (BODY or another DIV) has selection turned off, you can't turn it on just in the DIV. But if selection is on, you can turn it off in specific DIV elements.
{ e=e||window.event
s=e.srcElement||e.target
s.onselectstartSaved=s.onselectStart
s.onselectstart=null
s.attachEvent('onmouseup',restore)
}
function restore(e)
{ e=window.event||e
s=e.srcElement||e.target
s.detachEvent('onmouseup',restore)
s.onselectstart=s.onselectstartSaved }