insert / upsert into a splayed table

What is the best way to insert data into a splay table but avoid duplicates? For a non splayed table I can use upsert which will overwrite the current entries but will not generate duplicates

for instance will update the 09:30:00 entry to 42.0

<font color='"#000000"' face='"monospace,' courier new><span style='"line-height:'>t1 : ([ti:09:30:00 09:31:00]; p:101.5 33.5) </span><span style='"line-height:'>`t1 upsert (09:30:00; 42.0)</span><span style='"line-height:'><br></span></font>

In a splayed case what is the best/efficient way to achieve the same functionality - for instance below I get a duplicate entry but I would only like to update the entry.

<font color='"#000000"' face='"monospace,' courier new><span style='"line-height:'>`:c:/q/db/t/ set ([] ti:09:30:00 09:31:00; p:101.5 33.5) `:c:/q/db/t/ upsert (09:30:00;42.0)</span><span style='"line-height:'><br></span></font>

Any advice appreciated

David

http://code.kx.com/wiki/JB:KdbplusForMortals/splayed_tables#1.2.4_Built-in_Operations_on_the_Persisted_Splayed_Table

Hope this helps

Regards
Showvik