How to write your own formula for conditional formatting?

Question

Google Sheets

There is a table consisting of several columns, for example 15.
Rows, for example, 20.
The task is as follows:
If cell C11 has a value of 100%, then the entire row number 11 (all cells in this row) is filled with color up to column "O" inclusive , but not more.

Answer 1

It may be enough to set up conditional formatting:

1. specify fill range
   
2. select custom functions
   
3. enter the function with the $ sign. This will force the entire line to be flooded
   

Answer 2

=И(
     ДВСCЫЛ("RC3";0)=1;
     СТОЛБЕЦ(ДВСCЫЛ("RC";0)<=СТОЛБЕЦ($O$1)
  )

,where INDIRECT("RC 3 ";0)=1 - 3 column (C)
INDIRECT("RC3",0)= 1 - =100%
COLUMN(INDIRECT("RC",0)<=COLUMN($ O $1 ) - up to and including the "O" column.