Along of the lines of what Prashant is saying...
Create a public property on your control:
Public Property myval
...
End Property
Then you load your control similar to how you have done but to a declared variable of the control class type:
Dim ctlMyControl As MyControl
ctlMyControl = CType(LoadControl("mycontrol.ascx"), MyControl)
Then you can set your property:
ctlMyControl.myval = "valuehere"
Then add the control to the placeholder:
Placeholder1.Controls.Add(ctlMyControl)
-
Peter