Find if a number is part of a range

Hi there,
I have a little bit of an issue. I need to find out if a number is part of a giving range.
I have the following code:

Dim dt as new datatable
Dim dtrow as datarow
Dt = loaddata()

For each dtrow in dt.rows then
Dim str as string = dtrow.items("unit").tostring()
Dim range as string = dtrow.items("range").tostring()
'Some how in here I need create a function or sub that will tell me if the str is in my range or not
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The datatable has units like this
5.000
6.00000
1.0000
23000.00
And ranges are like this:
1
2 to 5
6 to 20
21 to 50
50 >
For the bigger numbers those are dollars amounts and behave the same way.
How can I do this?
Thanks