Parsing a string into numeric values

Hi,

Its been a long while since I've done much with excel/VBA. I'm wondering if anybody could help point me in the right direction.

The user enters a series of numeric values (comma seperated) into a text box called txtmeasures on a form.

These values are all stored as a string in a variable called 'txtval'.

I want to be able to take each individual value stored in that string and compare it to a range.

The range is pre-determined based on a previous selection from a dropdown box.

The range can appear as any of the three scenarios below:

> X

< X

X < Y < Z

Where X and Y and Z are integers


A calculation is then carried out based on the following:

X = [Sum only those values that fall within the specified range] / [Sum all entered values]

My real issue comes from parsing those values stored in 'txtval' and figuring out how to store and compare them to the range and thus obtaining the result of my calculation.

If I can get any help that would be greatly appreciated.

Thank you!