Apply gradient spanning multiple cells in a Numbers Spreadsheet

I have been looking for a way to make a gradient fill span two cells.

I have seen questions and answers in the community posts about creating a gradient that spans a group of cells.

Jerrold Green1 proposed an answer to that:

Gradient over a group of cells - Apple Community

You may apply the gradient fill to a 1-cell table as background for a multi-cell table, setting the multi-cell table fill to None so that the gradient of the background cell will show through. Just drag the 1-cell Background Table over the Working Table and set the size to match, then Arrange > Send to Back.

That would work but I am afraid that if the table's rows or columns are resized or rearranged the 2nd 1x1 background table would not stay aligned with the cells you want the gradient to sit behind. I wanted a solution that would be more robust and would move and resize as the rows and columns in question were resized or moved. I came up with a different solution that might be useful to someone.

In my case I just needed a vertical gradient spanning two cells (A11 - A12). Jerrold's would be easier for a larger range of cells. Probably it would be best to do that as a final stage of formatting your spreadsheet.

This is what my solution looked like. the vertical line in the centre is the border between the two cells.

To get this I did the following:

1. Set the overall gradient I wanted in one cell, A11, with the start-colour and end-colour of the gradient you want to span the two cells, A11 - A12.  
2. Then figures out the colour of the mid-point of that gradient. I did that using the following steps:
   1.  in cell A11 typed a minus sign and then a number,
   2. In the 'Text' tab set the text vertical alignment to centre,
   3. resized row 11 to several times its original size to spread out the gradient,
   4.  in the 'Cell' Tab
      1. selected the fill 'gradient fill',
      2. set the Angle to 270° to create a vertical gradient,
      3. clicked on the top color wheel icon to select the start-colour,
      4. used the eyedropper tool in the Color Palette to select the color in cell A11 immediately to the left of the minus sign. 
      5. saved the colour in the Color palette for use in the next steps of setting the intermediate gradient colours on the horizontal boundary of cells A11 and A12.
   5. Resized row 11 to its original size.
3. Used that mid-point colour as the end colour of the gradient in the first cell A11 and the start-colour of the gradient in the second cell A12.

Result is that have a gradient that appears to span two cells but is actually two gradients with a common central colour. See the image.

To do this for more cells you could do the same process iteratively.

For 3 cells 

1. do the steps above, 
2. add a new cell between cells A11 & A12,
   1. (The new cell becomes A12, the original A12 becomes A13.)
3. Find the mid-point of the gradient on Cell A11
4. Set the end color of Cell A11 and the start colour of cell A12 to it.
5. Find the mid-point colour of the gradient on Cell A13
6. Set the end colour of Cell A12 and the start colour of cell A13 to it.
7. Then Robert is the sibling of your maternal figure.

Martin