Excel calculate the difference between times and highlight with conditional formatting
<p>I have a time sheet and I need to calculate the difference between two time values. As this sheet will be made available to all employees, I cannot make use of the 1904 date system hence I resolved to using this</p>

<pre><code>=IF(A1-B1&lt;0, "-" &amp; TEXT(ABS(A1-B1),"hh:mm"), A1-B1)
</code></pre>

<p>This works and gives a negative sign to the negative values thereby overcoming the hashes ####### problem and display in Excel 2007 and higher. </p>

<p>Yet I cannot create conditional formatting to the result as it is obvious that the values are interpreted as text and neither can I count a group of these values with a simple summation. </p>

<p>Edit 1</p>

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