Excel 2007 : Choice of statistical method

I want to find whether there is a significant difference between 9 groups with regard to one dependent factor.

The groups are divided based on how many times they have reserved a service (independent variable X). The dependent factor is a score which goes from 0 to 100. My hypothesis (H1) is that the higher the number of received services (X) is, the higher the score will be (dependent variable Y).

Hence, both the X and the Y are continous variables.

My question is which statistical method I should use to figure this out? And also I will probably need help with the method in excel and the interpretation of the results...

The data are attached.

The groups are highly variable in size, where the majority have received a low number of services.

Thank you very very much in advance for your help!