How to remove ":" in file name while using Variable substution

Hi ALL

I am using file adapter and I what to create file name dynamically by acesssing PO number and time stamp from the payload using variable substution.

But the problem is I am getting ":" in time stamp field value and it is not acceptable for file name .

So could you please tell me a way that I can remove this ":" from that particular field value and create the file name dynamically.

Note 1)Add Time stamp option will not help me as we require a time stamp of particular zone.

2) Dynamic Configuration code is also not use full as I am using 1:n file creation