I have 0,4*A1 in a cell (as a string). How can convert this \"string formula\" into a real formula and calculate its value, in another cell?
0,4*A1
The best, non-VBA, way to do this is using the TEXT formula. It takes a string as an argument and converts it to a value.
For example, =TEXT ("0.4*A1",'##') will return the value of 0.4 * the value that's in cell A1 of that worksheet.