Formula for Value-Combination (FIXED, LEN) doesn't work with values with changed decimal places

I wrote a formula to combine a value and its standard deviation in one cell. Cell A1: 2.945 Cell B1: 0.003 formula: =FIXED(A1;(LEN(B1)-2))&"("&(B1*(10^(LEN(B1)-2))&")") Result: 2.945(3) In my ar...