Validating Datain textboxes

[lenin42001]

Help i've just done a basic calculator with three textboxes a label & a button, basically when you add a number in textbox1 to the one in textbox2 it appears in textbox3 .........now the question asks to check if the user has typed in something appropriate . It says double click on txtnum1 use right hand list box to find Validating( ) event, then modify event stub so it looks like this
If Not IsNumeric(txtNum1.text) Then e.Cancel =True End if

Please where does the last data go to ? Where is the validating event. I've tried to put it in the text box but it doesnt work. Where is Validating on the right hand side. I can't see it anywhere..........All help gratefully recieved.

[iburyak]

When you double click on a text box in design view you will see 2 boxes with different choices on the top. Left hand box shows your text box name and left box shows Change. Open box where you see change and scroll down to Validate.

[lenin42001]

When you double click on a text box in design view you will see 2 boxes with different choices on the top. Left hand box shows your text box name and left box shows Change. Open box where you see change and scroll down to Validate.

Thanks i got stuck