guys.. i'm tryin to create a calculator..

there's a field for me to type the formula

eg. 1 + 3 / (2*2)

so..when i submited the string

a = "1+3/(2*2)"

can i just straight convert the a to a math formula and give me the output

P/s : i wanna do something like the EXCEL, we can use type in the formula and get the instant output

thanx in advance