Validating vb user form text box - help!

Hi,

I have a nifty little userform designed to retrieve & hold six values in textboxes taken from a worksheet based on an input that the user enters into the first textbox on the form ('uniqueref') which is then searched for in column A. The code is as follows:

Private Sub uniqueref_AfterUpdate()
lastrow = Range("A65536").End(xlUp).Row
findrow = Range("A1:A" & lastrow).Find(uniqueref.Value, Cells(1, 1)).Row
For I = 1 To 6
UserForm1.Controls.Item("TextBox" & CStr(I)).Value = Cells(findrow, I).Value
Next I
End Sub

The userform also has the ability to rewrite any amended values on the form back to the worksheet using:

Private Sub Ok_Click()
For I = 1 To 6
Cells(findrow, I).Value = UserForm1.Controls.Item("TextBox" & CStr(I)).Value
UserForm1.Controls.Item("TextBox" & CStr(I)).Value = ""
Next I
End Sub

This all works well however I want to adapt the code so that:
a) the form will only accept a numeric value in the 'uniqueref' textbox on the userform
b) the form will only accept a value that exists in column A of the workheet
c) if the above occurs, a msgbox will be displayed saying either "must be a number!" or "number does not exist!"
d) also, that the uniqueref field will be cleared and focus reset so that the user can attempt a new (valid) input

I'm guessing I need a Private Sub uniqueref_BeforeUpdate(ByVal Cancel As MSForms.ReturnBoolean) routine but I'm a bit out of my depth here . Can anyone help please?

Thanks in anticipation of assistance.

Hi Holger, thanks for the response.
Both work great, except the Set Focus. Not sure why.
Any ideas?

It worked! Thanks!!!

Sorry I solved this too soon. There's a small problem, I've got ten records listed unique ref 1-10. I don't know why, but the data results for 10 are showing when the uniqueref entered is both 1 and 10.

2-9 are all correct. It's just 1 (the first record) that's a problem. 1 is on row 16, 10 on row 7 (2-9 in between). There's no other values in column A. Any ideas??

You beauty !!! :-)))