Search parameters to find inside formulas

I use this line to search for a chain or a digit in the sheet

Cells.Find(C, ActiveCell, xlValues, xlPart, xlByColumns, xlPrevious).Activate

and it works fine; but in cells with formulas it doesn't search inside the formula; only in the total value.
Which parameter must I change so it will search also inside the formula?
I've tried xlFormulas in place of xlValues; but then it searches only inside formulas skipping other cells

Thanks for any help