Convert fractions to decimals

Hello All
I keep my racing odds in fractions. I like to change them to decimals.
In one cell called A3 I keep the data, and would like the decimal value in A4.

If the first digit is L then the decimal value should always be -1.00.
eg L100\30 should be -1.00 in A3.

However, if the first digit is W, than I like the decimal value to be in cell A3
to two decimal places.
For Example.
W10\3 should be 3.33 in A3
W3\1 should be 3.00.in A3
W10\11 should be 0.91
W11\4 should be 2.75

Any help would be welcome.
(I am using Excel 2002)

Maybe:

=IF(LEFT(A3,1)="L",-1,MID(A3,2,FIND("\",A3)-2)/RIGHT(A3,LEN(A3)-FIND("\",A3)))

Dom

Thanks Dom
That seems to work ok. Thanks very much