<?xml version="1.0" encoding="utf-8"?>
<root>
  <item
    znam_avg="                   123"
    val_avg="456"
    flag_minus="-1" />
  <item
    znam_avg="    789"
    val_avg="abc"
    flag_minus="1" />
</root>

<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="xml" />
  <xsl:template match="/root">
    <root>
      <xsl:for-each select="item">
        <xsl:if test="@znam_avg!=999999">
          <td>
            <xsl:value-of select="@val_avg" />
            <xsl:if test="@flag_minus=-1">
              <xsl:value-of select="'(-1/'" />
              <xsl:call-template name="left-trim">
                <xsl:with-param name="string" select="@znam_avg" />
              </xsl:call-template>
              <xsl:value-of select="')'" />
            </xsl:if>
            <xsl:if test="@flag_minus=1">
              <xsl:value-of select="'(1/'" />
              <xsl:call-template name="left-trim">
                <xsl:with-param name="string" select="@znam_avg" />
              </xsl:call-template>
              <xsl:value-of select="')'" />
            </xsl:if>
          </td>
        </xsl:if>
      </xsl:for-each>
    </root>
  </xsl:template>
  <!-- trim-left recursive template -->
  <xsl:template name="left-trim">
    <xsl:param name="string" select="''" />
    <xsl:variable name="tmp" select="substring($string, 1, 1)" />
    <xsl:choose>
      <xsl:when test="$tmp = ' ' or $tmp = '&#xA;'">
        <xsl:call-template name="left-trim">
          <xsl:with-param name="string" select="substring-after($string, $tmp)" />
        </xsl:call-template>
      </xsl:when>
      <xsl:otherwise>
        <xsl:value-of select="$string" />
      </xsl:otherwise>
    </xsl:choose>
  </xsl:template>
</xsl:stylesheet>

<?xml version="1.0" encoding="utf-8"?>
<root>
	<td>456(-1/123)</td>
	<td>abc(1/789)</td>
</root>

<?xml version="1.0" encoding="windows-1251"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="xml" />
  <xsl:template match="/root">
    <root>
      <xsl:for-each select="item">
        <xsl:if test="@znam_avg!=999999">
          <td>
            <xsl:value-of select="@val_avg" />
            <xsl:if test="@flag_minus=-1">
              <xsl:value-of select="concat('(-1/', @znam_avg, ')')" />
            </xsl:if>
            <xsl:if test="@flag_minus=1">
              <xsl:value-of select="concat('(1/', @znam_avg, ')')" />
            </xsl:if>
          </td>
        </xsl:if>
      </xsl:for-each>
    </root>
  </xsl:template>
</xsl:stylesheet>

<?xml version="1.0" encoding="utf-8"?>
<root>
  <td>456(-1/                   123)</td>
  <td>abc(1/    789)</td>
</root>