Countif function referencing a dynamic cell

Hi!

Hoping to get some help on this. I've got a cell (Q4) that I want to count the number of datapoints within a certain date range (C4 & C5) in a certain worksheet (selected from a drop-down list in C6). The formula I have in Q4 at the moment is:

=COUNTIFS('wind speed'!$A$4:$A$58875,">="&start_date,'wind speed'!$A$4:$A$58875,"<="&end_date)

What I'm trying to do is to change the parts in bold in the formula above to represent the value in cell C6 (which is dynamic as its selected from a drop-down list).
The range on the worksheet is the same for all worksheets.

Any ideas??

Thanks!

Genious! I was looking at the INDIRECT function, but had no idea how to apply it!

Thank you!!