Create new record and fill regarding field via url

Hi,

I am trying to create a new appointment via url as described here:

https://msdn.microsoft.com/en-us/library/gg334375%28v=crm.6%29?f=255&MSPPError=-2147217396#BKMK_ExampleWindowOpen

I have tried it with following extraqs parameter:

regardingobjectid={someguid}&regardingobjectname=adventure works&regardingobjecttype=account

with following exception:

System.InvalidOperationException: CRM Parameter Filter - Invalid parameter 'regardingobjectidtype=account' in Request.QueryString

and with following extraqs

pId={someguid}&pName=advanture works&pType=account

I got this exception:

Parameter name: Expected 'Integer' data type for 'pType' parameter in 'Request.QueryString'

I have no more idea what can I do to prefill a regarding field.

Thanks for your help