title: Excel VBA : Compare Values Within a column for all other rows having same identification key in another column
body: <p>I have a jumbled time series data as I have shown above in the first image. What I want to do is to check and flag is some of the keys do not change value over time.</p>
  <p>Actual Data</p>
  <p><a href="https://i.stack.imgur.com/T48CJ.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/T48CJ.png" alt="Image 1- Actual Data" /></a></p>
  <p>First I tried splitting the data for every unique key as separate time series into different worksheets but I have over 17k unique keys so rather impossible to split them as individual worksheets and process them all due to ram issues.</p>
  <p>To explain the situation better, for example as you can see for the key - <strong>123abc</strong> in column A, I have different values in <strong>some number</strong> (column C) at different points in time(column B).(Image 2)</p>
  <p>No static values</p>
  <p><a href="https://i.stack.imgur.com/SokWD.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/SokWD.png" alt="Image 2 - No static values" /></a></p>
  <p>But in the case of key - <strong>431iow</strong> the values in <strong>some number</strong>(column C) was same for 3 consecutive quarters. (Image 3)</p>
  <p>Some static values</p>
  <p><a href="https://i.stack.imgur.com/rHDiW.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/rHDiW.png" alt="Image 3 - Some static values" /></a></p>
  <p>I would want to try and flag the rows which didn't change over last quarter, and leave others blank and add this flag variable as a new column.(Image 4)</p>
  <p>Flags/Desired Outcome</p>
  <p><a href="https://i.stack.imgur.com/wZ3k9.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/wZ3k9.png" alt="Image 4 - Flags/Desired Outcome" /></a></p>
  <p>And also make a consolidated file with unique entries from Column A with just flags as shown in Image 5.</p>
  <p>Flag/Desired result</p>
  <p><a href="https://i.stack.imgur.com/Ppc0p.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Ppc0p.png" alt="Image 5 - Flag/Desired result" /></a></p>
  <p>Can someone help me with this very specific issue?</p>
  <p>Any help is appreciated.</p>