how to set length and postion for repeat-x and scroll background-image?

I have an to set background image. it is a red line under the input value.

background-attachment:scroll;
background-color:#FFFFFF;
background-image:url("../images/errorLine.gif");
background-position:left bottom;
background-repeat:repeat-x;

the input value is like "123; 456; 789;". the red line cover all the string, its length is the same as the input width.

Is there any way to make the red line only under the "456;"?

Is there anyway to do it by CSS?

Thanks a lot.

Best regards,

Ryanivanka

I'm not entirely sure this is what you need, but why not use border-bottom?

123 <span style="border-bottom: 1px red solid">456</span> 789

for a display: inline element, the border will always be underneath the text, and wrap across lines.