two decimal when I use String

[kvelentz]

Hi, I am very sorry for my English .
I'm new to ireport and I want to add two decimal in each price (for example 3.4  I want to be 3.40)
If I have BigDecimal is easy , just put in the pattern '###0.00'
But I have a problem when there is String. I have searched a lot but I could not find a solution.
Thank you in advance
Kostas