There is a related question on Stack Overflow that has a helpful answer:
Generally: the way to refer to "this" cell is to enter notation for the upper-left corner of the range being formatted. For example, if the range is C1:C, then C1 means "this cell".
So, for example, if you want to highlight all cells containing formulas in the range
A1:J10, then you can use the formula
=ISFORMULA(A1) and apply it to the range
A1:J10. The important part is that the cell reference in your formula (e.g. A1) matches the upper-left cell in the range you are formatting (e.g. A1:J10).
Note also that for the
ISFORMULA() function in particular, it is possible to specify either a cell or a range for the parameter, though regardless whether you use a cell or range, it only looks at the first cell anyway:
ISFORMULA returns TRUE if cell is a cell that contains a formula. If cell contains a range of cells then TRUE will be returned if the first cell in the range contains a formula. All other values will return FALSE.
So, you could also use the formula
=ISFORMULA(A1:J10) to format your range. Note that this works with normal ranges (e.g. B2:F30), but not with infinite ranges (e.g. B:F).