Windows 7: Disk Management - Extending/spanning a Striped Dynamic Disk, how?

I hope someone can help me with this issue but let me first explain my situation...

I''ve been running my PC with 3 HDD's:
1x PCI-E SSD running an internal RAID-5 with 2 Partitions ( Partition C:\ & D:\ )
2x SATA HDD running as Striped Dynamic Disks with 4 Partitions ( Partition E:\ F:\ G:\ & H:\ )

The last Partition ( H:\ ) is my big Data Folder which is now becoming a little cramped so I was planning to increase it's size by adding 2 additional HDD's into the system.

Question:
Is it possible to Extend Partition H:\ onto these 2 new HDD's while running them as a Striped Dynamic Disks using the Windows 7 Software RAID solution?
If Yes - How can I do this?
If No - Is it possible with a dedicated RAID-Card?

Thanks in advance.