Check that a string only contains numbers

Hi guys,

I have a text box that is used to enter commands into my application.  One of these commands is to allow the user to select a new frequency.  Frequencies are always entered in the format 1xx.xxx where each x represents a number only.  The format for the command is '.freq1 1xx.xxx".  

I split the string down to, what should be, a resulting two strings of three characters each.  How do check that the user has only entered numbers?  This is important otherwise I'll end up attempting to set the frequency incorrectly.

Many thanks.
LVL 16
Ady FootSharePoint ConsultantAsked:
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sirbountyCommented:
Something like...

If Not IsNumeric(txtFrequency.Text.SubString(7,7)) Then
 MessageBox ("Not a valid frequency!")
 Exit Sub
End If
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Ady FootSharePoint ConsultantAuthor Commented:
Great stuff and the quick response is much appreciate....this was holding me up a little.

Thanks a lot for your help.
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sirbountyCommented:
Glad I could help! :^)
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