User Form Required Fields

I have a user form and I need the fields to be required to be filled before it can be closed. Right now I have. . .

Private Sub BTNSave_Click()

TargetRow = Range("A" & Rows.Count).End(xlUp).Row + 1
X = TargetRow - 3
DT = Format(Now, "mm/dd/yyyy hh:mm:ss AM/PM")



Cells(TargetRow, 4).Value = TXTWhatsYourName.Text
If TXTWhatsYourName = "" Then MsgBox ("You Must Enter A Name!")

Cells(TargetRow, 7).Value = TXTDescription.Text
If TXTDescription = "" Then MsgBox ("You Must Enter A Description!")

Cells(TargetRow, 5).Value = TXTWOname.Text
If TXTWOname = "" Then MsgBox ("You Must Enter A Work Order Number!")

Cells(TargetRow, 6).Value = TXTPartsNumber.Text
If TXTPartsNumber = "" Then MsgBox ("You Must Enter A PartNumber!")

Cells(TargetRow, 8).Value = TXTPartsQTY.Text
If TXTPartsQTY = "" Then MsgBox ("You Must Enter A Quantity!")

Cells(TargetRow, 9).Value = TXTNeededbydateandtime.Text
If TXTNeededbydateandtime = "" Then MsgBox ("You Must Enter A Date and Time!")

Cells(TargetRow, 10).Value = DDUnitOnFloor.Value
If DDUnitOnFloor = "" Then MsgBox ("You must choose from Unit on the Floor!")

Cells(TargetRow, 11).Value = DDReason.Text
If DDReason = "" Then MsgBox ("You must choose a Reason!")

Cells(TargetRow, 12).Value = DDManufacturingArea.Text
If DDManufacturingArea = "" Then MsgBox ("You must choose a Manufacturing Area!")

Cells(TargetRow, 13).Value = DDDPUEntered.Text
If DDDPUEntered = "" Then MsgBox ("Was DPU Entered?")

Cells(TargetRow, 15).Value = DDDiditgotodesign.Text
If DDDiditgotodesign = "" Then MsgBox ("Did it go to design?")

Cells(TargetRow, 16).Value = TXTWhoDidDPU.Text
If TXTWhoDidDPU = "" Then MsgBox ("Who Did DPU?")



Cells(TargetRow, 1) = X
Cells(TargetRow, 3).Value = DT
Cells(TargetRow, 2).Interior.Color = vbGreen

Me.Hide
Unload Me
ActiveWorkbook.Save

End Sub

I would like everything before Cells . . = X to be required before it can be closed. How is this done? Thank you!