Solved this by a friend,
I could make a shared function on the searchCustomerfrm form that returns the value that you expect from the form:
Public Shared Function GetCustomer()
Dim PopUpCustomer As New searchCustomerfrm
If PopUpCustomer.ShowDialog() = DialogResult.OK Then
Return Val(PopUpCustomer.DGVCustomer.Item(1, PopUpCustomer.DGVCustomer.CurrentRow.Index).Value)
Else
Return Nothing
End If
End Function
On the DGVCustomer_CellContentDoubleClick write this:
Private Sub DGVCustomer_CellContentDoubleClick(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) Handles DGVCustomer.CellContentDoubleClick
Me.DialogResult = DialogResult.OK
End Sub
To call the searchCustomerfrm from OrderFormFrm:
txtCustCode.Text = searchCustomerfrm.GetCustomer