Post your code and explain what you mean. By child do you mean it descends from, or it contains another user control plus more controls? Either way the user control is a strongly typed class so just add public methods.
In the parent user control .ascx.vb file the function is as listed below:
Sub DisplayApprovalChainList(ByVal dsALTmp As WFInterfaceWS.dsStepLocation_v2)
lblApprovers.Visible = False
lblNoRecords.Visible = False
dlApprovalChain.Visible = True
dlApprovalChain.DataSource = dsALTmp
In the child user control .ascx.vb file the function with in the parent user control i.e., DisplayApprovalChainList(ByVal....) needs to be accessed with in the function as listed below..
Private Sub ShowApprovalChainControl()
Dim dsAL As WFInterfaceWS.dsStepLocation_v2
dsAL = Me.dsApproverChain