Resize Bootcamp Partition

I set up Windows 7 on Bootcamp. I am running OSx Yosemite in a Macbook Pro (mid 2010).

After I set up Windows 7 and installed all my work programs, I realized the 45GB I dedicated is not large enough. I need about 55-65GB.

When I go to resize the partition in Disk Utility the option to drag the Mac OSx partition is not available. I cannot select to add more partitions or resize either partition. The only option it gives me is the ' - ' button to delete the Bootcamp Partition which is the last thing I want to do. The "Partition Layout", "Size", and "+" options are all greyed out.

Is there a way to resize this bootcamp partition given the information above?