I want to create a program an ArcMap add-in commond

[Abdul_HameedKhorami1]

I want to create and program an arc map add in commend in vb.net. to calculates a measure of gender structure ((Male_pop/FEAMLE_POP)*100 in a GenderStr field. I am getting an error I have included both my code and error message I am getting. I am wondering if anyone can help me what is the problem to solve this error?

thanks

[Abdul_HameedKhorami1]

its its double!

[RebeccaStrauch__GISP]

Have you looked thru the sample ins the help?

Calculate Field examples—Help | ArcGIS for Desktop 

It does have sample for VB (and python)

[ModyBuchbinder]

I am not sure the expression is the problem here.

If you just give something simple (for example ".Expression = 1.23") does the code works?