In a named region have a descending number if a condition is met.

[HeinD]

If(condition; "value of cell to the left"; "value of cell to the left"-1)

I tried: IF(condition; LAMBDA(namedregion;0;1);LAMBDA(namedregion;0;1)-) it did not work.
I need the named region to get a blue edge around the region to show the formula is everywhere the same;
IF(condition;A1;A1-1) works great but does not give the blue line around the region.