Apply Conditional Format to a range of cells based on other Cells

I want to conditionally format (put a red border around the cell) cells in the range D10:D100, if the corresponding value in another column (say T10:T100) equals a reference value in cell S1.

So for example: D10 gets formatted if T10 = the value in S1; D11 gets formatted if T11 = the value in S1, etc.

Now, I can do this to format a single cell, but how to I extend this to the full range (D10:D100), given that I don't want to mess up the (fixed) formatting already present throughout column D? Eg. If I setup the conditional format on cell D10, and then do a copy and 'paste special' of 'formats' over D11 to D100 - I destroy the existing formats on D11 to D100. Similarly, if I do a right click on D10 and drag "formatting only", I destroy the existing formats on D11 to D100. So I need either:
- A way to specify the formula in the conditional formatting such that it applies over D10:D100, OR
- A way to extend the conditional formatting from D10 to the rest of the range in a way that is "additive" - ie. does not interfere with the preexisting formatting in the range.

Many Thanks

That does the trick! Thanks.