Non - numeric hand vane values

Holebase accepts non-numeric data (eg >140) into the [InSituVane.Result] field.

Using the expression;

if(len([InSituVane.Result])>0,'HVP=' + text(fixed([InSituVane.Result], 0, false)),'') + if(len([InSituVane.Result])>0 and len([InSituVane.Residualresult])>0,', ','') + if(len([InSituVane.Residualresult])>0,'HVR=' + text(fixed([InSituVane.Residualresult], 0, false)),'')+'kPa'

will only output numeric data.

Non-numeric data isn't output.

Am I using the wrong data test "len > 0" in this expression?