This error is because you removed the extensions from the conditions file Choose_block_decimals.xlsx. You are trying to use the Decimals_Block1_072418.xlsx spreadsheet, but as the extension has been removed, it will not work because the browser does not know what the file type is.
So, you cannot insert the name of a conditions file into itself, because then it tries to read itself for infinity. But, you can insert the name of a conditions file that is different. For example, my cond.xlsx file attached, can call condition file A.xlsx, and from A.xlsx I can access the myFraction variable.