option explicit error converting system.web.ui.controls to system.web.ui.webcontrols.textb

How would I rewrite this so that I do not get the error: "Option Strict On disallows implicit conversions from 'System.Web.UI.Control' to 'System.Web.UI.WebControls.TextBox'."

 Sub doinsert(ByVal sender As Object, ByVal e As DataGridCommandEventArgs)
 If e.CommandName = "insertupdate" Then
 Dim custst As String
 Dim aprst, mayst, junst, julst, augst, sepst, octst, novst, decst, janst, febst, marst As String
 Dim aprtxt, maytxt, juntxt, jultxt, augtxt, septxt, octtxt, novtxt, dectxt, jantxt, febtxt, martxt As TextBox
 aprtxt = e.Item.FindControl("txtapr")
 aprst = aprtxt.Text
 aprtxt.Text = "0"
 maytxt = e.Item.FindControl("txtmay")
 mayst = maytxt.Text
 maytxt.Text = "0"
 juntxt = e.Item.FindControl("txtjun")
 junst = juntxt.Text
 juntxt.Text = "0"
 jultxt = e.Item.FindControl("txtjul")
 julst = jultxt.Text
 jultxt.Text = "0"
 augtxt = e.Item.FindControl("txtaug")
 augst = augtxt.Text
 augtxt.Text = "0"
 septxt = e.Item.FindControl("txtsep")
 sepst = septxt.Text
 septxt.Text = "0"
 octtxt = e.Item.FindControl("txtoct")
 octst = octtxt.Text
 octtxt.Text = "0"
 novtxt = e.Item.FindControl("txtnov")
 novst = novtxt.Text
 novtxt.Text = "0"
 dectxt = e.Item.FindControl("txtdec")
 decst = dectxt.Text
 dectxt.Text = "0"
 jantxt = e.Item.FindControl("txtjan")
 janst = jantxt.Text
 jantxt.Text = "0"
 febtxt = e.Item.FindControl("txtfeb")
 febst = febtxt.Text
 febtxt.Text = "0"
 martxt = e.Item.FindControl("txtmar")
 marst = martxt.Text
 martxt.Text = "0"
 testlabel3.Text = aprst
 If radiocustomer.Checked = True Then
 strcust = DropDowncust1.SelectedItem.Text
 strcustid = DropDowncust1.SelectedItem.Value
 Else
 strcust = prospecttxt.Text
 strcustid = "0000"
 End If

Probably you need this cast at relevant points:

aprtxt = CType(e.Item.FindControl("txtapr"), TextBox)
Thank you, that is what I needed.