Your formula is doing division and the divisor (denominator) is zero. The result of such expression is either infinity or Nan (not a number). If denominator is an array, this warning message means that one of denominator array elements is zero.
There are many ways to prevent this, namely:
1. Checking denominator for zero prior to division and avoid division in such cases (works for scalars, not arrays):
for( i = 0;
i < BarCount; i++ )
{
denom = High[ i ] - Low[ i ];
if( denom != 0 )
result[ i ] = Close[ i ] / denom; // only divide
when denominator is not zero
}
2. Adding small value to denominator (works for both scalars and arrays)
result = Close / ( High - Low + 1e-9 );
3. Using Nz() function to convert non-a-numbers and infinites to resonable value (by default zero). Note that this won't supress the warning but will make the result finite:
result = Nz( Close / ( High - Low ) );
4. Changing zero values in denominator array prior to division using IIF() function
denom = High - Low;
result = Close / IIf( denom != 0,
denom, 0.001 );