How to make sure the datatype is float in asp?

Hello, I have the sequence of flash to asp to database. And I can get the values from flash in asp by using request.form …

and saving to database by the coding

conn.Execute “INSERT INTO TF_pic VALUES(’”&idnumber&"’,’"&galleryF&"’,’"&frontgalleryx&"’,’"&frontgalleryy&"’,’"&frontrotationgl&"’,’"&galleryFx&"’,’"&galleryFy&"’)"

But when I save those datas to database, there is error like
Type mismatch: ‘[string: “259.409865642173”]’

It refers to the galleryFx variable. Does it mean that the database recognised the value as string but not the float value as I expected.

I defined the datatype for the galleryFx as float datatype, then how can I make sure that the data are really saved as float by making sure the &galleryFx& is really a float value?

Thanks a lot in advance!