=IF(C3<0, (C3-C2)/B2*100 & " (" & C3-C2 & ")","")

This is the function I used at this moment. but it has some problem. all
data in column B & C are number format with no more than 4 decimal digits, so
that both (C3-C2)/B2*100 and C3-C2 are still number, especially without
decimal digits control.

The result I expected is for example when C3 = 2.5350 and C2 = 2.5060 and B2
= 2.456, the result shows me "1.18 (0.0290)". 2 decimal digits in the first
part, 4 decimal digits in the second part. Besides, it is possible that C3 is
smaller than C2, so that the negative number is also expected if it happens.

Who can help me to realize this result?

Thanks go to anyone who think about my troubles!

Best Regards,
Viesta Wu