I have an excel file with a number of different work sheets say,
wksheet1, wksheet2 and wksheet3.
Is it possible to use the hyperlink function to switch between work
sheets? For example, if I'm on wksheet1 and want to switch to wksheet2
can I click on a hyperlink which is written as wksheet2 to switch to
wksheet2.

One way is to start with
Insert Hyperlink
then in the dialog box
- click "Place in this document"
- choose a sheet
- type in the cell reference
- type in "text to display."

Using the hyperlink() function is a different approach: more flexible, but
more complicated. For example, the following links to cell A23 of Sheet2 of
the workbook:
=HYPERLINK("["&SUBSTITUTE(LEFT(CELL("filename"),
FIND("]",CELL("filename"))-1),"[","")&
"]Sheet2!A"&(22+1),"text")
Save the file before using this formula (otherwise CELL("filename") is
undefined).
There might be a shorter version.

For details of hyperlink, see Excel's built-in Help.

(I have Excel 2003.)