Hopefully you have a Main (parent) form, where to place the tool strip, that you already set the IsMdiContainer property to True.
When you launch the additional forms from this one, you set the MdiParent property of the children form pointing to the Main form.
Dim F as new frmChildForm1
F.MdiParent = Me
In each child form, you should add a Public sub or function that deletes the data related only to this child form.
Public Sub Delete
' Delete whatever you need
On the Main form, when the user clicks the tool strip 'Delete' button, you can cicle over the children forms
For Each ChildForm as Form In Me.Children
Inside the loop you can place validations to determine wich one is the child form and call the Delete sub
If ChildForm Is frmChildForm1 Then
ElseIF ChildForm Is frmChilForm2 Then
' Do Nothing