How about this:
Dim _pisdk As PISDK.PISDK = New PISDK.PISDK() Dim pt1 As PISDK.PIPoint = _pisdk.Servers("mypiserver").PIPoints("sinusoid") pt1.Data.UpdateValue(20, "*")
You would include the name of your PI Server in place of "mypiserver". This examples pushes the value 20 to tag sinusoid.
The PI SDK documentation is full of examples on how you can use the updatevalue() method to push a value to a tag.
Also check that that the date you're inserting has an on-line archive covering that interval, and that it has available space; you may need to reprocess that archive.