Change client-side javascript variable value from server side

On page load, I have the below code to set the totalcount variable value to 25. On a button click, I would like to change this value to row count of a grid. How do I change this?

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

Dim sb As StringBuilder = New StringBuilder()
 sb.Append("<script type=""text/javascript"">")
sb.AppendFormat("var Label1 = '{0}';", "Less")
sb.AppendFormat("var Label2 = '{0}';", "More")
b.AppendFormat("var {0} = '{1}';", "TotalCount", 25)
sb.Append("initPages();")
sb.Append("</script>")
Me.Page.ClientScript.RegisterClientScriptBlock(Me.GetType(), "searchscript", sb.ToString())
End Sub

Protected Sub Continue_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Continue.Click

End Sub