The only thing I can think of is to split your text layer, so that each value produces a different shape.
Alternatively, you could recreate the entire counter using shapes, then drive the opacity of each shape based on the expression. So you’d have shapes in the units column, duplicated and repositioned or the 10s etc… then on each shape, use something like:
var numArray = String(thisComp.layer("0 Outlines").effect("Random Number")("Slider")).split('');
if (numArray[2] == 1) {
100
} else {
0
}
This is assuming that the slider is produces decimals. In this case, I tested on the value 4.1
4 was in the 0 position in the array, ‘.’ in the 1 position and numArray[2] was the decimal.
If numArray[2] equals 1 and the shape is the 1 character, show it, else hide it.